The Mining Magazine, Vol. 42, No. 4

Mining Magazine

\lu,Hi , Oil i .'to i fit ¿ E d ito r : W . F. W h i t e . A s sista n ts: St. J . R .C . S h e p h e r d , A .R .S .M ..D .I.C ., F .G .S .;

F . H i g h a m , A .R .S .M ., M .Sc., F.G .S.

P u b l i s h d o n t h e 1 5 t h o f e a c h m o n t h b y M i n i n g P u b l i c a t i o n s , L i m i t e d , a t S a l i s b u r y H o u s e , L o n d o n ,

E.C.

.

fe! p h one : ; • >politan 8938 T e leg ra p h ic A d d r e s s : Oligoclase. C o d e s : M c N e ill, b o th E d itio n s , & B en tley.

‘ ( N ew ' o r k : A m er. I n s t. M. & M .E . QTiBcrDiPTmv i 12s - p e r a n n u m , in c lu d in g p o s ta g e .

‘ • * * ' * •» 0 r F , C E S ( f t , . > : 3 6 0 , N . M i c h i g a n B l v d . S u b s c r i p t i o n j v & ^ , 3 p e r >n n u n l ( i n 6c l E d i l l g 6 p 0 S t a g e .

Vol. XLII. No. ⁴ . L O N D O N , A P R I L , 1930.

C O N T E N T S

Ed i t o r i a l

'v res ... 194

In d E else D . . on S i lv e r ; T h e D e a th of L o rd I i Rti lan R a ilw a y s ; C o n tro l o t M a la y a n

¡'in i nies The C h a n n e l T u n n e l.

ning Congress... 194

I'll* ' i \ 1 ' ■ ngs of th e th ir d E m p ir e M in in g Congi i A frica a re d e a lt w ith .

Ms ta!s . - l b - . >ry.

th t \ M-. ■ . ig of th e I n s t i tu t e of M e ta ls a re review ed.

The Education of the Engineer ... 197

T he qu estio n w h e th e r th e B ritis h - tra in e d e n g in e e r is securing as good a p p o in tm e n ts a s so m e of h is fellow s of o th e r n a tio n a lity is c o n sid ered .

Re v i e w o f Mi n i n g ... 1 9 8 Ar t i c l e s

A Field Test w ith a New Seismograph

A new e le c tric se ism o g ra p h is d e s c rib e d a n d a n a c c o u n t is given of a s u rv e y m a d e o v e r a k n o w n a re a to te s t th e a p p lic a b ility of th e m e th o d to th e lo c a tio n of sim ple s tru c tu re s .

Uranium in Cornwall . . . . / / . G. Dines 213

The a u th o r d e scrib es b rie fly th e h a b its of th e u ra n iu m m in erals a n d s u m m a riz e s th e o c c u rre n c e s in th e W e st of E n g la n d .

Magnesite Deposits in Serbia

A . Ignatieff 217

The a u th o r d e scrib es d e p o s its of m a g n e s ite in S e rb ia n M acedonia a n d g iv es a t h e o r y fo r th e g en esis of th e m ineral.

The S tantrg Lead-Zinc Mine, Yugo­

slavia ... 222

A p ag e of p h o to g ra p h s to s u p p le m e n t th e a rtic le in th e J a n u a r y issue.

Bo o k Re v i e w s

G reenly a n d W illia m s, “ M eth o d s in Geological S u rv e y in g ” T . Eastwood 223 Ne w s Le t t e r s

Johannesburg ... 224

W a a ik ra a l M ine to b e C lo sed ; G old L o s t in T a ilin g s ; A n I m p o r ta n t M e rg e r ; A n U n d e v e lo p e d C o p p er F ie ld ; A N e w R h o d e s ia n C o a lfie ld ; A C e n tra l G eological B u re a u ; A C o n c e n tra tio n P ro c ess D is p u te ; S o u th A fric a n K i e s e l g u h r ; M u rc h iso n M edal fo r D r. A. L . H a ll ; S t a te R e v e n u e fro m M ining.

4 — 3 1 9 3

PA G E

Ipoh

M a la y a n S ta tis tic s for 1929 ; C h ief M in e ra l P r o d u c ts of th e F .M .S . ; T in O re S ta tis tic s ; P o w er S u p p ly .

V anco u v er

G e n e ra l O u tlo o k ; N ew P o w e r P r o je c t ; B o u n d a ry .

T oronto

S u d b u r y D i s t r i c t ; P o rc u p in e ; K ir k la n d L a k e ; R o u y n .

C a m b o rn e

M in in g a n d C h in a -c la y L e a ses ; A R e c e iv e r A p p o in te d a t D o lc o a th .

Pe r s o n a l ... 231 Tr a d e Pa r a g r a p h s ... 2 3 2 R o b in s V ib ra tin g S c re e n s... 232

“ S u p rem e ” V ib ra to r Screen a n d C onveyor 233 T ilm an sto n e R o p e w ay ... 235 C rossley Oil E n g in e s ... 236 T y p e 60 H u m -m e r E le ctric S c r e e n ... 238 Me t a l Ma r k e t s ... 23 9 St a t i s t i c s o f Pr o d u c t i o n ... 241 Pr i c e s o f Ch e m i c a l s... 2 43 Sh a r e Qu o t a t i o n s ... 2 4 4 Mi n i n g Di g e s t

T h e N o ra n d a S m e lte r

W . G. Boggs and J . N . Anderson 245 T h e Geology of th e B o u ld er B elt, K algoorlie

F . L . Stillw ell 252 So lu tio n of C u p rite

J . D . S u lliva n and G. I.. Oldright 254 T h e A lask a J u n e a u C o n c en trato r

P . R . B radley 254 Sh o r t No t i c e s... 2 5 5 Re c e n t Pa t e n t s Pu b l i s h e d... 2 5 5 Ne w Bo o k s, Pa m p h l e t s, e t c... 2 5 6 Co m p a n y Re p o r t s... 2 5 6

B a la g h a t G old M ines ; C row n M ines ; D u r b a n R o o d e - p o o r t D e e p ; E a s t R a n d P r o p r i e t a r y ; G e d u ld P r o p rie ta r y M in es ; G e ld e n h u is D e e p ; G o p e n g C o n so lid a te d ; G o v e rn ­ m e n t G old M in in g A re a s ; L a n g la a te E s t a t e G o ld ; M ey er a n d C h a rlto n G old ; M o d d e rfo n te in B ; M o d d e rfo n te in D e e p ; N e w K le in fo n te in ; N e w S t a te A re a s ; N u n d y d ro o g M in e s ; R a n d fo n te in E s t a t e s ; R o b in so n D e e p ; R ose D e e p ; S im m e r a n d J a c k M ines ; V a n R y n D e e p ; V illage D e e p ; W e st R a n d C o n so lid a te d ; W itw a te rs r a n d D e e p ; W itw a te rs r a n d G old.

Di v i d e n d s De c l a r e d ... 2 6 0 Ne w Co m p a n i e s Re g i s t e r e d... 2 6 0

E D IT O R IA L

R E M A R K S here last m o n th on th e benefit t h a t w ould accrue to th e B u rm a C orporation arising o u t of th e In d ia B udget proposals were a little prem ature. I t seems th a t th e an ticip ate d effect of th e d u ty on silver im p o rts is to be offset b y th e im position of an excise d u ty of exactly th e sam e am ount on th e m etal indigenously produced.

W IT H th e passing of Lord B alfour th e co u n try lost n o t only a g reat sta te s­

m an b u t one who did m ore for th e prom otion of science an d k ep t in closer touch w ith its progress th a n a n y of his colleagues. T he in itial steps w hich resulted in th e foundation of th e N atio n al Physical L a b o ra to ry were ta k e n during his period of office as F irst Lord of th e T reasury an d he was also in stru m en tal in founding th e D e p artm en t of Scientific an d In d u stria l R esearch.

T H E proposed Sm oia-K afue sh o rt cut has again beer; side-tracked—in rail­

w ay parlance— an d th e Commission, referred to here in J a n u a ry last, w hich m akes this re p o rt also finds against th e construction of a connexion betw een B eit Bridge and W est Nicholson. As for th e W alvis B ay line, Mr. P o tte r disagrees w ith Mr. W allace’s contention th a t th is is, justified. In the m eantim e th e B echuanaland an d S outhern R hodesian G overnm ents are likely to have a survey m ade of th e last-nam ed project.

M E E T IN G S of th e M alayan Tin, Southern M alayan, an d Southern P erak com­

panies were called for A pril 14 a t w hich it w as proposed to a lte r th e articles of association to ensure th e m aintenance of B ritish control, th e reason p u t forw ard being th a t th ere h a d been heav y buying of shares on foreign account, followed b y pressure to secure representation. T he changes proposed also included th e reten tio n of th e services of th e present board for a period of a t least five years. I t was subsequently announced th a t th e m eetings h a d been cancelled. _______________

O NCE again th e C hannel T unnel Scheme is before th e public w ith th e issue of th e rep o rt of th e G overnm ent C om m ittee app o in ted in April last to consider th e economic aspects of th e proposal. The

M a g a z i n e

for O ctober an d N ovem ber, 1913, a n d J u ly an d D ecem ber, 1916, throw s light b o th on th e geological an d on th e engineering aspects of th e project. Its construction m ay be possible from these standpoints, b u t

w hether it is econom ically sound is a n o tiu : m a tte r. M any engineers will b. disposed to- agree w ith Lord E bbisham in his di- ■ nr from th e views of th e rem ainder of the . > m m ittee.

One fu rth e r fact m ay be noted th e m ilitary' objection seems to be less ins -te n t

T h e E m p ir e M in in g C on gres

The th ird E m pire M ining and M t ,rx a]

Congress m ay in a sense be regarde-J as having com m enced w hen th e legates left London on M arch 7, th e le

W aterloo sta tio n an d sub ¡eently at S o u th am p to n being in every v • w orthy <>i th e occasion. The Congress ’ as. -tawevet, form ally opened on M arch 24 pc . v b y th e E a rl of A thlone, th e Go r,i, >• «>... a ,|

of th e U nion, who, in welcom r. d- tio n on behalf of th e Governm people of S outh Africa, rem arked on part played b y th e m ining and ...et,i hirgxal industries in th e developm ent

as well as in th e whole of mode ihzation, and com plim ented th e C ouncil; oust P a' tu in stitu te s on th e invaluable v

doing. As no d o u b t his hearers were aware, this was no p erfu n cto ry utterance, for L ord A thlone, like o th er m em bers of the R oyal fam ily, speaks from a profound knowledge of m an y of th e problem s under­

hung these m a tte rs. The welcome formalities concluded, Sir E rn est O ppenheim er delivered his presidential address an d dealt w ith the need for th e consistent encouragem ent of E u ropean settlem en t in such p a rts of South Africa as were suitable for w hite occupation and instanced u n alienated areas in the highlands where m ining could continue its w ork of creating a lastin g E u ropean civiliza­

tion. J u s t as m ining has developed the U nion, so it bids fair to do in Northern Rhodesia, and in his opinion a vigorous developm ent policy for th e whole sub­

con tin en t was th e b est m eth o d of civilizing th e native. F inally, he drew an interesting parallel betw een th e present w ealth and superlative p ro d u c tiv ity of th e R an d gold- field and th e p robable fu tu re prosperity of th e R hodesian copper-field an d made a plea for sim ilar group control of th e latter.

A second session of th e Congress opened in Joh an n esb u rg on M arch 31, u n d er the presidency of D r. H. Pirow , th e Government Mining Engineer, a t w hich H o n o rary Member­

ship of th e In stitu tio n of Mining and M etallurgy was conferred on Mr. P. M.

Anderson, th e president of th e Transvaal

Cham ber of Mines, an d it was decided to

A P R IL , 1930 195 accept th e in v itatio n t o , hold th e fourth

Congress in A ustralia in 1933.

W ith reg ard to th e papers presented at the various sessions, it is unnecessary to a ttem p t here m ore th a n a sum m ary survey of th e field covered. The papers m ay conveniently be divided into sections, of which some notes are appended concerning the m ore im p o rta n t from th e view point of readers of th e

U nder the heading of reviews and occurrences are a num ber of reports, covering th e period 1927-9, b y C anadians, on th e m ineral industry of th e D om inion and its provinces, to which m ay be added a paper on th e mining industry in Southern R hodesia and one on the Lydenburg platin u m areas. Papers on mining deal alm ost exclusively w ith R and practice, if we include as sub-sections papers dealing w ith shaft sinking, breaking ground, hoisting and hauling, ventilation, and power. W hile few of these cover new ground, y et some disclose details and present data not previously obtainable. F o r example, on the subject of tunnelling a t W est R and Consolidated, Mr. C. S. McLean reveals th at as m any as 10,000 drills are dealt w ith by a central statio n in one 8-hour shift, while Mr. W. G. C. Nixon, dealing w ith high-lift pumping, describes the practice of pum ping settled sludge in single lifts of 1,200 feet instead of baling. Mr. W. Eldson Dew’s paper on w inding a t great depths is a valuable supplement to tw o recent textbooks on this subject and a pap er by Mr. C. L. B utlin on shovelling and tram m ing indicates new economies possible in underground practice.

In the v entilation sub-section a paper by Mr. Jam es B oyd on th e estim ation of dust in mine air deals w ith a subject of which the literature is sparse. Ore-dressing and m etallurgy are covered by eight separate contributions. Included here is a useful historical review of flotation practice by Mr. H. L. Sulm an, proposals for w ater con­

centration tests b y Professor B. W. H olm an, and a p articularly valuable paper b y Messrs.

W. J. Gau and J. I. Jam eson on th e m etal­

lurgical practice a t Leeuw poort Tin Mines.

A paper on platin u m m etallurgy b y Messrs.

F. W artenw eiler an d A. K ing contains interesting flow-sheets. In th e field of prospecting an d sam pling Professor T ruscott presents a thesis on th e com putation of ore reserves which will be ab stracted in our next issue, as will certain other papers in this series, and Mr. J. Allan Howe deals w ith the conservation of drilling records.

As to th e mines, works, and o th er places of interest visited in th e course of th e tour, these have already been referred to in the

Ma g a z i n e

for Septem ber last. The elaborate

arrangem ents m ade for th e reception and hospitable tre atm en t of th e delegates have w orked as adm irably as was to be expected.

In this connexion m ention m ay be m ade of two nam es in particular, Captain J. H.

Jefferies, th e general secretary, and Mr.

George Reid, th e m anager. In conclusion it is only necessary to repeat w hat has been sta te d here concerning previous conferences and tours, th a t b y far th e m ost im portant result of these m eetings of Em pire m embers of the profession, an d others interested who join therein, is th e o p portunity of studying a t first h an d th e various phases of th e work in progress, while a t th e same tim e enjoying all th e benefits of friendly intercourse and inform al discussion, nothing being b etter calculated to advance the well-being and future prosperity both of the enterprise and of th e individual.

M e ta ls in H isto ry

The p ast m onth has witnessed the appear­

ance of three papers dealing either directly or rem otely w ith his+ory. Two of these were presented a t th e March m eeting of the In stitu tio n , when Sir H arold C arpenter and Dr. M. S. Fisher introduced " A S tu d y of the C rystal S tructures of N ative Copper,” which deals w ith th e m etal in geological tim e, while Dr. T. A. R ickard, in outlining the sto ry of

“ Copper Mining in Cyprus,” confined himself to historical time. The last-nam ed au th o r also presented the th ird paper a t the annual m eeting of th e In stitu te of Metals on March 12, under the title of “ The E arly Use of the M etals.” H istory is ever a m a tte r of interest as m uch to th e scientist as to the laym an, as was evidenced b y th e discussion which these respective studies prom oted, and th e final paper referred to deserves special considera­

tion as being one of the few occasions on which m etallurgists and anthropologists have got together.

I t will be rem em bered th a t two years ago Professor Carpenter, in collaboration with Dr. S. T am ura, presented to the In stitu tio n an account of a prelim inary investigation of th e inner crystal stru ctu re of some native m etals, a brief account of which was given in

the

for April, 1928. The m ain

purpose of th a t work was th e application of

m etallographic technique to th e interpretation

196 T H E M IN IN G M AGAZINE of stru ctu re s of n ativ e m etals w hereby it

was hoped th a t some light m ight be th ro w n on th e origin and geological h isto ry of n ativ e m etal deposits. As th e au th o rs pointed out in their reply to the discussion arising from th a t paper, th e stu d y was sim ply an in tro ­ d u cto ry survey of a v ery wide field. In th e ir investigation of n ativ e copper th e au th o rs of th e present paper have proceeded a step fu rth er and lim ited the field of inquiry to one p articu lar m etal. One im p o rtan t applica­

tion of th e results o btained was noted im m ediately by several speakers an d th a t was th e light which would be throw n b y such w ork on th e tem p eratu re of form ation of m inerals paragenetically associated w ith th e n ativ e m etal. Dr. W. R. Jones, for exam ple, in referring to the w ork of W right and Larsen (which was discussed, in th e light of investiga­

tions by B ram m all and H arw ood, in the

Ma g a z i n e

for March, 1927), pointed o u t th a t

th e results ob tain ed b y these workers in th e use of q u artz as a geological therm om eter were difficult to duplicate an d it was evident th a t for certain lim ited conditions a stu d y of th e cry stal stru ctu re of n ativ e copper would be of im m ense im portance. W h at is more significant is the fact th a t copper is b u t one of several m etals and m etalloids which occur in th e native sta te and separate studies of these elem ental m inerals will be capable of application to a series of differing geological conditions. This led D r. H. C. Boydell to ask th e au th o rs seriously to consider a stu d y of n ative silver, as it seemed to him th a t this w ould be of incalculable benefit to Canadian geologists in th e investigation of such im p o rtan t m ineral deposits as those of the Cobalt d istrict of Ontario. Briefly, it m ay be sta te d th a t th e au th o rs have reached th e conclusion th a t th e whole of the tw en ty specimens included in th eir exam ination h a d been form ed a t low tem perature, either by rhythm ic precipitation from a gel, by the replacem ent of pre-existing m inerals, or by deposition from aqueous solution, all of which conclusions are additional support to theories of origin which have been suggested by geological workers. The question of electrical deposition was raised in th e discussion by Dr. Jones, who referred to the w ork of F ox on m ineralized fissures in Corn­

wall. I t was fu rth er evident th a t recon­

stru ctio n of th e m etal after deposition had left unm istakable signs, certain specimens, for instance, being in a sta te of strain, re- crystallizing when h eated a t tem peratures betw een 500° C. and 600° C. and becoming

homogeneous a t a te m p eratu re below 800° C., th u s showing th a t none of th e specimens had ever been a t a tem p e ratu re n ear th e melting point. In y e t o th er cases it has been possible, b y a careful stu d y of th e behaviour of m ineral inclusions during progressive heat- tre a tm e n t, to show th a t certain specimens h a d undergone th erm al m etam orphism sub­

sequent to deposition. A ltogether the paper is an excellent exam ple of th e illum inating assistance to oth er w orkers w hich is so often afforded by a specialized stu d y of a particular problem .

Of th e tw o papers b y D r. R ickard the more interesting discussion was raised by that before th e I n s titu te of M etals, in which, as already rem arked, some em inent anthro­

pologists took p art. I t is evident from the w ealth of bibliographic references cited that th e a u th o r has ta k e n a g reat deal of pains to assemble his d a ta and, while all will not agree w ith his every conclusion, he has undoubtedly k n it together an interesting story from the tim e w hen prim itive m an first discovered the n ativ e m etals— copper, gold, silver and m eteoric iron—an d b eat a n d fashioned them into shape for o rn am en tal or implemental use to th e tim e when, in a la te r stage of developm ent, he discovered by chance the effect of his cam p fire in producing metal from the earth an d so h it upon the idea of sm elting as d istin ct from m elting, which Dr. R ickard rig h tly em phasizes as the most m om entous factor in th e whole story of m an’s conflict w ith n atu re. The discovery of bronze by th e chance sm elting of a copper ore containing cassiterite and in a similar m anner brass were successive steps and in due tim e the idea of th e effects of h eat, draught, charcoal, and fluxes having been grasped th e sm elting of iron from its ores followed.

E vidence is adduced to show th a t the use of iron preceded th a t of bronze in some civiliza­

tion and this encourages th e a u th o r to dispose of th e successive stone, bronze, and iron ages of history. There is now adays a general agreem ent w ith the subdivision of tim e into two ages—th e Stone Age and th e M etal Age.

The Stone Age is held to cover th a t period of

tim e when m an was as y et unaw are of metals

and to be succeeded by a tran sitio n period

when the n ativ e m etals becam e known and

appreciated and this led to th e age when the

use of m etals and fo rtuitous alloys became

extended consequent upon th e discoveries of

the effects of fire upon the earth . The author

pays well-deserved trib u te to th e w ritings of

th e late Professor W. G ow land on this

A P R IL , 1930 197 fascinating subject, while in the discussion

reference was m ade by one of the speakers to the w ork of Professor V. Gordon Childe as one of th e archeologists who h ad dealt with m etallurgy in his recent book on the bronze age.

T h e E d u c a tio n o f th e E n g in e e r

Consideration of th e extensive scale on which th e developm ent of th e copper deposits of N orthern R hodesia has been planned, economically to exploit th e v a st tonnages of ore available, an d th e fact th a t the super­

vision of these operations has been m ainly entrusted to engineers train ed in the U nited States m ust carry w ith it th e realization th a t the m anagem ent of m any mines under British control and situ a te d w ithin the British E m pire is in the hands of engineers of other th a n our own n atio n ality . The development and exploitation of th e low- grade porphyry copper deposits of America, the scale of operations and th e exact technique dem anded to ensure profitable extraction of values, and above all the resultant ap titu d e of men train ed in such large-scale environm ents have n o t u n n a tu r­

ally led those responsible for th e opening up of com paratively low-grade copper properties to tu rn a t once to th e U nited S tates for technical direction. Indeed, it is difficult to see w hat other choice could have been made.

Copper deposits of this character, however, are not the only ones in the Em pire which have been developed and are being m anaged for us. More th a n one im p o rtan t gold mine, a p art from those of th e R and, are entrusted to th e m anagem ent—and, it must be adm itted, capable m anagem ent—of American-trained engineers and th e same is true of a num ber of base-m etal enterprises.

T hat the directorate of a B ritish com pany would choose a foreigner as superintendent of its property in preference to a B riton—

if a com petent B riton were available— it is impossible to believe ; it is, in fact, common knowledge th a t in several cases posts have been filled b y other nationals only after many B ritish applicants have been in ter­

viewed. If the foregoing m ay be regarded as a fair statem en t of th e present position it is surely w orthy of exam ination.

The possibilities for practical training in metalliferous m ining in G reat B ritain are, it will be generally adm itted, extrem ely limited.

Apart from th e Cornish mines, the only properties which are, or have been, worked

on large-scale lines are the hem atite bodies of th e north-w estern counties. The Jurassic iron-ores are bedded deposits of regular character, th e working of which can generally be run in accordance w ith norm al colliery practice. F o r experience on such a scale as will create self-confidence in tackling opera­

tions of any m agnitude it will be adm itted th a t a B ritish stu d en t m ust go outside these islands. As this is only possible in a lim ited num ber of cases during th e period of stu d e n t­

ship it is evident th a t foreigners—and particularly Americans—trained in close proxim ity to and spending their vacations on im portant metalliferous mines have a decided advantage over their average fellows in this country. On th e other hand, their course of instruction a t a m ining school com­

pleted, m ost B ritish graduates go abroad for their first appointm ent and doubtless some of them proceed to mines where there are opportunities for supplem enting their technical education. I t would seem, how­

ever, th a t some additional explanation is required to account for th e failure of engineers of B ritish training to reach positions con­

trolling operations of m agnitude.

This tra in of tho u g h t raises a question w hether th e p rim ary education system of this country is in any w ay responsible. While we do n o t feel we are justified in analysing a system which is the envy of the world, it m ay be excusable for us to endeavour to throw some light on th e effect of school trad itio n on training for the profession of engineering and more particularly th e highly specialized profession of mining engineering. Recently Professor T ruscott m entioned one of our less w orthy national characteristics, th a t of a tendency to praise “ artistic indolence,”

referring, am ong other things, to th e pre­

valent youthful a ttitu d e of regarding hard w ork as som ething to be avoided, a dangerous conception if carried to a late period in life.

The product of th e universities and technical in stitu tes in this country is a complex blend of these and other w orthier types.

In th is connexion there is th e possibility th a t a particular college m ay obtain a bad rep u tatio n because of those “ work shy ” young m en—however m uch th ey be in a m inority—which it sends out into th e world.

A t a tim e when so m uch im portant develop­

m ent work is in progress w ithin th e Em pire

it seems desirable to focus a tten tio n on this

subject and if a more disappointing view

has been tak en th a n is justified no one

will be more pleased th a n ourselves.

R E V IE W O F M IN IN G

In tr o d u c tio n . — T he d ate of issue of

th e

alm ost synchronizes w ith B udget D ay an d th e general tone of business, which has lately shown im provem ent, will doubtless be ru led b y th e new conditions. In th e m etal m ark et th e price of tin has again been disappointing, th e relief an ticip ate d from restriction not y e t having m aterialized.

T r a n sv a a l.—The o u tp u t of gold on th e

R an d during M arch was 852,089 oz. an d in outside districts 37,281 oz., m aking a to ta l of 889,370 oz., as com pared w ith 818,188 oz.

in F ebruary. A t th e end of M arch th e num ber of natives w orking in th e gold m ines was 200,134, as com pared w ith 196,752 a t th e end of F ebruary.

The rep o rt of R and Mines, L td ., for 1929 showed a profit for th e year of £545,470 and

£511,288 was d istrib u ted as dividends, equal to 100%, th e same as for th e previous four years. The in terest in T rin id ad Lease­

holds is proving a profitable one and develop­

m ents on th e properties of th e N orth Venezuelan P etroleum Com pany and of th e Tocuyo Oilfields of Venezuela com pany are favourable. The rep o rt also sta te s th a t an in terest has been tak e n in certain m ining ven tu res in B olivia and it is understood th a t th e com pany is becoming interested in tin mining.

Good progress continues to be m ade w ith th e developm ent of th e E a st Geduld p ro ­ p erty , which is being carried on from th e east of th e Geduld P ro p rie ta ry workings.

The rep o rt for 1929 shows th a t progress during th e year am ounted to 17,305 ft. and while as y e t little ore has been blocked out com pletely th e w ork done indicates th a t partially-developed and probable ore am ounted to ab o u t 2,400,000 tons a t the end of the year. In March, 1929, it was decided to sink a vertical shaft and th e w ork was sta rte d th e following m onth, th e d e p th m a rk a t th e end of th e y ear being 460 ft. In a circular to shareholders issued later it is sta te d th a t developm ents continue to be so encouraging th a t a reduction p la n t is to be installed capable of tre a tin g 60,000 to n s per m onth. To m eet th e expense of installation 500,000 new ordinary shares are to be issued.

A serious accident a t th e Crown Mines tow ards th e m iddle of last m o n th resulted in th e d e a th of 28 natives and a w hite miner.

The natives were in a cage w hich broke aw ay an d crashed to th e b ottom of th e shaft, a distance of 1,600 ft.

C a p e C o lo n y .—A circular

to share­

holders of th e African A sbestos T ru st states th a t owing to th e financial position of the com pany it has been necessary to restrict m ining operations to th e ex tra c tio n of long- fibred m ineral. This will m ean th a t the developm ents on th e M unnik H ill property, where ore reserves were estim ated at 274,000 tons, will be tem p o rarily suspended.

D ia m o n d s.— An announcem ent in the

Legislative A ssem bly of th e U nion on M arch 26 by th e M inister of Finance revealed t h a t an agreem ent has been reached with regard to th e allocation of diam ond pro­

d ucers’ quotas and also th e sale of both the U nion an d S outh-W est A frica diamonds.

S o u th e r n R h o d e s ia .—T he

o u tp u t of gold during F e b ru a ry w as 43,385 oz., as com pared w ith 46,121 oz. in Ja n u a ry and 44,551 oz. in F e b ru a ry of 1929. Other o u tp u ts in F e b ru a ry were : Silver, 5,509 oz. ; copper, 108 tons ; coal, 92,437 to n s ; chrome ore, 21,049 tons ; asbestos, 4,126 to n s ; m ica, 10 tons.

The rep o rt of th e Globe an d Phoenix for 1929 shows th a t th e available ore reserves a t th e end of th e y ear were estim ated to be 51,400 tons containing 48,300 oz. gold, to g eth er w ith 49,100 tons containing 67,300 oz. in th e pillars. T he to ta l of 100,500 tons containing 115,600 oz. compares with 86,700 tons containing 111,700 oz. a t the end of th e previous year. D uring the year 72,369 tons of ore was crushed an d 60,225 oz.

of gold recovered, w hich is 15,705 oz. less th a n in 1928. N early tw o-thirds of this reduction is due to th e suspension of operation of th e sands p la n t during th e year, it having been found b e tte r p ractice to allow sands to accum ulate for a period an d th en to run the p la n t to capacity. D evelopm ent on the 15th level has revealed 615 ft. of ore, averaging 18-5 dw t. over 37-3 in., an d on th e 29th level ore was exposed for a distance of 130 ft., averaging 49-1 dw t. over 44-4 in. The limits of th is ore have n o t y e t been determ ined.

A circular to shareholders of Southern R hodesia Base M etals C orporation states th a t in th e q u a rte r ended M arch 31 last 535 tons of copper concentrates, averaging 67% copper, was produced, th e plant operating satisfactorily. I t is also stated th a t arran g em en ts have been m ade with M inerals S eparation, L td ., for th e construc­

tion of a copper segregation p la n t capable of

tre a tin g up to 50 tons of oxide an d mixed

198

A P R IL , 1930 199 oxide-sulphide ore per day, a large tonnage

of such ore having already been developed.

Developments in the A laska m ine continue to be favourable and it is sta te d th a t from the north-east side of th e shaft 20 ft. has been driven in ore, full w idth unknown, averaging 7-2% copper as sulphide. In addition to th e sulphide there is present

1 -2% copper in th e form of oxide.

N orthern R h o d e sia .—The six th progress

report of the R hodesia-K atanga Company states th a t up to the end of J a n u a ry a t the Kansanshi mine some 2,000 ft. of driving has been done along th e west, north, and east sides of th e hill on th e 100 ft. and 150 ft.

levels. This w ork has shown th a t there is a zone of replacem ent ore, of varying w idth, extending around th e hill on the dolomite- schist contact. On th e 100 ft. level this ore has been proved over a length of 300 ft. and assays 15-8% copper, and sim ilar values were obtained on the 150 ft. level. A new reef has been discovered to the east of A reef and development w ork is in progress, having so far revealed 105 ft. of ore averaging approxim ately 4% copper over 4 ft. of lode.

It is said th a t values are increasing to the north. W ork on the sulphide reefs continues to show favourable results.

Shareholders of R hodesian Congo Border Concession have been inform ed of th e results of two bore-holes situ a te d west of the N’Changa boundary. The first of these, N.E. 33, situ ated on the southern fold-limb in the Chingola area, entered ore a t 215 ft.

and from 215 ft. to 250 ft. th e assays averaged 10-35% copper. A t 260 ft. the hole entered a second ore-zone and from 260 ft. to 275 ft. the core recovered assayed 18'33% copper, while th e sludge assayed 7-73%. The second hole, N .E. 17, lies nearer the N ’Changa pro p erty and is said to have entered ore a t 988 ft. and to 1,061 ft. the ground assayed 6-38% copper. This hole is,

at 1,071 f t., still in ore.

The Bw ana M’K ubw a Com pany announce th at a cross-cut a t the 450 ft. level from No. 1 vertical shaft on th e N ’K ana m ine has penetrated th e ore-body, which over a true w idth of 22-8 ft. averaged 5-40% copper.

A u stra lia .—The decision of the Common­

wealth G overnm ent to pay a prem ium on gold equivalent to th e selling exchange rate less 25% has, in effect, introduced a bounty on gold. This will v a ry w ith th e exchange, but am ounts approxim ately to 4s. an ounce.

The interim rep o rt of th e Broken Hill South for the half-year ended Decem ber 31 last

shows th a t the estim ated surplus for the period is £154,000, as com pared w ith £140,000 in th e corresponding period of 1928.

A pproxim ately one-third of the surplus was derived from th e production and sale of zinc concentrates. D uring th e period m entioned 165,660 tons of ore, averaging 14-3% lead, 11-0% zinc, and 5-2 oz. silver, was tre a te d , and 33,922 tons of lead con­

centrates, averaging 66-1% lead, 6-4% zinc, and 23 oz. silver, an d 30,227 tons of zinc concentrates, averaging 49-2% zinc, 2-1%

lead, and 1-6 oz. silver, were produced.

The first section of the tailings re tre a t­

m ent p lant on the Golden Horseshoe came into operation a t the beginning of F eb ru ary an d ran in te rm itte n tly during th e m onth.

The ground treated am ounted to 13,232 short tons an d yielded gold w orth £2,854.

In d ia .—The report of the Ooregum Gold

Mining Company for 1929 shows a slight decrease in the ore reserves, which a t the end of th e year were estim ated to be 270,788 tons. D uring th e year 69,889 oz. of gold were obtained from 165,445 tons of ore milled, 11,887 oz. from 220,555 tons of tailings re­

treated , 555 oz. from old mill plates, and 152 oz. from 398 tons of ore m ined and milled by the N undydroog Company, m aking a to ta l of 82,483 oz. The average value of ore milled was 8-68 dwt. per ton. The n et profit for th e year was £76,556, a reduction of £23,371 as com pared w ith the previous year. D uring th e year 2s. per share was distrib u ted on the Preference and Is. per share on the O rdinary shares.

M a la y a .—The report of the Temengor

Tin Mining Com pany for th e year ended Septem ber 30 last shows th a t developm ent of th e p ro p erty is proceeding smoothly.

Owing to exceptional drought, hydraulicking operations were som ewhat restricted, b u t it is expected th a t as soon as w eather con­

ditions perm it work will be possible on a full scale. The o u tp u t of tin concentrates during th e financial year was approxim ately 63 tons and th e value of th e ground per cu. yd. was 2-53 lb. The w orking of the experim ental stam p b a tte ry has shown th a t there is a large q u a n tity of rock available for treatm en t b y this plant. The capital of th e com pany is to be increased to £300,000.

A t a m eeting of shareholders of Am pang (Perak) Tin D redging, held on M arch 31 last, it was resolved th a t th e com pany should go into v o lu n tary liquidation.

I t is proposed to reduce th e capital of the

S tra its Trading Company from $6,750,000

200

T H E M IN IN G MAGAZINE to $900,000, by w riting down th e value of

each share of $7'50 to $1, and refunding in cash the balance of $6’50 per share.

P a n a m a .—The fourteenth progress report

of th e P an am a C orporation confirms the favourable developm ents a t th e Mina B lanca mine, H atillos. The m ineralized fissure is of m uch g reater w id th th a n h ad previously been supposed. Crosscuts are being actively driven an d it is sta te d th a t gold values are no t lim ited to th e gold-lead vein. T he exten­

sion of this has been located for 3,000 ft.

n o rth w ard s, prospect assays showing 66s.

gold per ton, th e to ta l value of th e ore being

£8 per ton. A pilot p la n t is to be erected and th e results obtained w ill largely d ete r­

mine th e course of fu tu re work. A t the Rem ance m ine it is estim ated th a t ore reserves averaging 33s. in gold per to n are im m ediately available in sufficient q u a n tity to supply th e m ill for tw o years. W ork on th e E l M ineral and Cana concessions is also well advanced, th e design of the necessary p la n t for th e form er being under consideration, while hydraulic p lan t is being installed on th e la tte r.

B o liv ia .—The rep o rt of P atin o Mines and

E n terp rises for 1929 shows th a t th e ore reserves, excluding dum p m aterial, a t th e end of th e year were estim ated to c o n tain 82,606 tons of fine tin , as com pared w ith 71,462 tons a t th e end of 1928. D uring the year 795,052 tons of ore, averaging 3-71%

tin , were developed, and 703,592 tons con­

taining 3-94% tin mined. The cost of pro­

duction of concentrates has been reduced by 7s. 3d. to 53s. 6d. per ton. T he acquisition of th e tin-sm elting p la n t of W illiams H arvey and Co. is sta te d to have cost £1,332,000.

L ater, all rights under th e W illiam s H arvey agreem ent were tran sferred to G eneral Tin Industries, an Am erican Com pany, on the condition th a t th e la tte r com pany assum ed th e obligations of th e co n tra c t and sold to th e P atino Com pany fully-paid G eneral T in In d u stries shares equal in value to the o rd in ary and ex trao rd in ary reserves Si the P atin o Mines, which is £634,995.

V e n e z u e la .—An agreem ent has been

concluded betw een B olivar V enezuela Gold Mines, L td ., an d New Goldfields of Venezuela, L td ., w hereby th e two com panies are to be am algam ated. The basis of th e m erger is such th a t each shareholder in th e form er com pany will receive one share of th e New Goldfields com pany for every share held in B olivar V enezuela Gold Mines. A t th e same

tim e the capital of New Goldfields of Venezuela, L td ., will be reduced, th e issued

£1 share being w ritte n down to 5s. and the unissued shares being split into four shares of 5s. each. I t is proposed in due course to create 700,000 ad d itio n al shares of 5s. each, w hich will m ake th e to ta l authorized capital

£1,675,000. The am algam ation will enable th e reserves on th e B olivar Venezuela p ro p erty , which in th e neighbourhood of the Union S haft alone are estim ated a t 250,000 tons, to be conveniently exploited by the tra n sp o rt system an d m ill installed by the New Goldfields com pany.

S p a in .—The re p o rt of th e T harsis Sulphur

a n d Copper Com pany for th e year 1929 shows th e n et profit earned to be £182,739 and

£82,139 was brought forw ard from 1928, D ividends a t th e ra te of 12J% will absorb

£125,000 an d £115,000 is to be transferred to general reserve, leaving £24,878 to be carried forw ard. W ork a t th e mines was carried out u n in te rru p te d ly during the year, all th e production being from th e Calañas mine and from th e S ierra Bullones opencast a t Tharsis.

The dividends p aid b y th e Rio Tinto Com pany during 1929 equalled 55% on the capital increased to £2,125,000 in June last.

This com pares w ith 40% on £1,875,000 in 1928. The tra d in g profit for th e year was

£1,669,782 an d th e to ta l income £1,930,110.

The mines w orked sm oothly during the year, th e to ta l q u a n tity of ore delivered by the com pany being in excess of th a t for 1928, and all the copper produced found a ready m arket.

P o r tu g a l.—The

to ta l q u a n tity of ore broken an d raised from th e San Domingos m ine during 1929 b y Mason and Barry, L td ., was 222,685 tons, as com pared with 184,868 tons in 1928. Ore shipm ents during th e same period am ounted to 203,778 tons, as against 200,701 tons the y ear before. The profit realized on th e y e a r’s w orking was

£20,238. I t is proposed to p a y a dividend of 12J% , which will absorb £23,146, leaving

£19,413 to be carried forw ard, as against

£22,321 th e previous year.

C o n s o lid a te d M in e s S e le c tio n .—The

rep o rt for 1929 shows th a t th e profit for the year was £112,300, as com pared w ith £79,836 in 1928. The dividend is m ain tain ed a t 20%, which will absorb £100,750. T he dividend equalization account has been reduced from

£18,000 to £10,000 b y the tran sfer of the

difference to profit and loss account.

A FIELD TEST WITH A NEW SEISMOGRAPH

By C A P T . H . S H A W , M.Sc.

A new electrical seismograph is described and an account given of a survey made over a known area to test the applicability of the method to the location of simple structures.

In t r o d u c t i o n.—

In the last issue of the

Ma g a z i n e,

Professor

R ankine gave a

detailed description of th e construction and method of operation of a new portable seismograph m ade by th e Cambridge In s tru ­ ment Company for geophysical survey. I t may be appropriate, therefore, to describe the essential features of another seism ograph by the same m akers, which has been developed recently from th e in stru m en t previously

great depths, as reasonably short profiles suffice to reveal th e tectonic features which are known to exist, and com paratively small charges of explosive have therefore been employed throughout the tests. F or greater penetration and over longer traverses, or in less suitable ground it would have been necessary to employ bigger charges, b u t for these tests it was n o t considered desirable to increase the scale of the operations unduly.

Fi g. 1.— Ge n e r a l Pl a n o f Su r v e y.

described, and to give an account of field tests which have been carried out w ith this apparatus. The aim of these tests was to investigate the possibility of locating simple geological structures by m eans of the seismic m ethod of geophysical surveying, and to report upon the su itab ility for this purpose of the new seismograph. Through the courtesy of the H odbarrow Mining Company, who also provided the explosive and the requisite personnel, the survey was conducted over an area n ear Millom, in Cumberland, where the geological stru ctu re is well-known from borings, and over which a survey by the gravitational m ethod had previously been made. F o r th e p artic u lar purpose in view it was unnecessary in th is area to p en etrate to

De s c r i p t i o n o f t h e Ar e a.—

The region

over which the test was m ade was th e treeless sandy foreshore off th e village of H averjgg near Millom. In th is area the overburden is of glacial drift comprising a m ixture of sand, clay, and gravel, b eneath which is carbon­

iferous lim estone, and which in tu rn is underlain by conglomerate. In th is particular locality hiem atite occurs usually as well- defined masses in the lim estone, and is frequently found associated w ith faults. The sandy surface is fairly hard in places, b u t very soft and m uddy in others. In some places large patches of shingle are to be seen while considerable areas exist on which, alm ost as soon as th e tide has receded, the sand becomes very fine and loose.

201

202

T H E M IN IN G MAGAZINE A w ell-m arked fault crosses n ear th e

m iddle of th e area selected for these tests, as m ay be seen from Fig. 1 in w hich th e position a n d direction of th is fault, as deduced from a g ra v ita tio n a l survey, is shown, w hilst th e section shown in Fig. 2 indicates th e throw of th e fault as com puted from the g ra v ita tio n al results. T he position and th ro w of th is fault hav e subsequently been verified b y th e bore­

holes B .H . 63 an d B .H . 129. On th e dow n­

throw side of th e fau lt th e lim estone is over- lain bjr a considerable thickness of sandstone (about 260 ft.) and as th e velocity of seismic waves in sandstone is v ery m uch less th a n th e corresponding velocity in lim estone th e re is .good reason to believe th a t th is m ethod m ight furnish a practicable m eans of locating th e

te st on outcropping lim estone in order to determ ine th e velocity of th e w aves in that m edium . T his te s t was m ade on another portion of th e C om pany’s p ro p erty (near H odbarrow Point) an d w ill be described later.

Ap p a r a t u s.

—T he p a rtic u la r apparatus

em ployed in these te sts was a single-com­

ponent Cam bridge seism ograph of th e vertical type, kin d ly len t b y th e m akers for the present survey. T he vib ro m eter portion of th is in stru m e n t resem bles v ery closely the a p p a ra tu s described b y Professor A. 0.

R ankine in th e M arch issue of th e

and used in th e tests on Chobham Ridges during th e sum m er of 1929. T h a t instrum ent was, how ever, a p u rely m echanical one, in

. GLACIAL -SANDS (oe»««’TT - 1o) '

.

n e w r e d.'s a n dSt o n e . - G : . : . ' •" "• (owuttva»3 : v - • t

. • • • ’• •• i •• •:..' V 1 . - ' ■ v '- '• ‘I**

•• AND- .V ; ^{CLAYS .}

r 71 ■

/ - \'4 \ — i - i — ,

— /

■_./ a - T - i- T '

x __ > L i m e s t o n e , ___ ~ T ~ / V .

_ , _ \ - J T Z - ' f

- 1 — q— i — — I / —/ — I -

~ T - ^ Z L 1 — i t *

F i g . 2 . — S e c t i o n a c r o s s a r e a a l o n g l i n e A B C , s h o w i n g p o s i t i o n a n d t h r o w o f f a u l t a s d e t e r m i n e d F R O M A P R E V I O U S G R A V IT Y S U R V E Y A N D F R O M B O R E - H O L E D A T A .

position of th e fault and probably also of in d icatin g its throw .

T he m ean velocities of elastic waves as given b y Sieberg are as follows :—

L im estone 16,400 ft. per sec.

Sandstone 5,850 ,, ,, ,,

w hile th e m ean value available for glacial d rift appears from o th er sources to be of th e order of 5,000 ft. per sec., so th a t th ere is little difference betw een th e velocities in san d sto n e and in th e overburden, although th ere is a m ark ed difference betw een th e lim estone velocity an d th e o th er two. The high-velocity of elastic waves in lim estone com pared w ith th e ir velocity in th e over­

b urden should also enable a d eterm ination of th e d e p th of th e lim estone surface to be d eterm ined b y th e refractio n m ethod along a su itab ly chosen traverse. T he velocity in th e glacial d rift is determ ined in practice w ith o u t difficulty, b u t in th e case of lim e­

stone it was necessary to conduct an au x iliary

w hich th e relativ e m otion of a heavy mass is m agnified b y a lig h t alum inium helm and tra n sm itte d b y a fine in ch n ed link to a v ertical axis carrying a m irro r which is th ereb y caused to ro ta te . In th e electrical ty p e of in stru m e n t w hich has been used in th e tests here recorded, th is m irror is replaced as shown in Fig. 3 b y a light coil of fine w ire supported v e rtically in a strong m agnetic field in w hich it is free to rotate a b o u t a v e rtical axis. T he coil is th u s caused to ro ta te b y every sm all m ovem ent of the vibrom eter m ass relativ e to th e base of the in stru m en t. T his principle h a s previously been em ployed in seism ographs b y Galitzin, A m bronn, R eu tlin g er, an d m ore recently by K archer and o th ers in Am erica, an d possesses a nu m b er of d istin c t adv an tag es over the pu rely m echanical form of in stru m e n t.

In th e p a rtic u la r in stru m e n t supplied, the

sm all electric cu rren t generated in this light

coil was m easured by a Cam bridge Portable

A P R IL , 1930 203 E lectro-cardiograph, a form of E inthoven

string galvanom eter enabling th e m otion of the vibrom eter m ass to be studied in con­

siderable detail. In 1903, E inthoven in tro ­ duced his string galvanom eter, in which, as its name im plies, th e v ita l p a rt is a strin g or fihre. This fibre is m ade extrem ely fine, and when suitably m ounted in a m agnetic field, responds w ith a high degree of accuracy to m inute electric currents. The ac tu a l m ove­

ments of the fibre are sm all and it is necessary to use a microscope in order to observe and record them . A t th e speeds and magnifica­

tion used for cardiograph w ork th e fibre m ust be strongly illum inated by a suitable lamp.

Fig. 4 shows diagfam m atically the arrange­

ment employed in th e present instrum ent.

The fibre C is illum inated b y th e filam ent of a 12-volt gas-filled silvered lam p M . The beam is projected on to a combined cylindrical lens an d m irro r G which reflects the beam back on to th e m irror X , and this in turn directs th e beam on to the cam era, the light passing through th e slit / from the cylindrical prism L in th e cam era to the photographic film. The fibre appears in front of the prism as a long vertical shadow about two m illim etres wide, th e p a rt crossing the cylindrical prism becoming a d ark spot in the b an d of light which falls on to the film. Thus if the film is given a m otion at right angles to th e cylindrical prism , th e whole w idth will be exposed except th a t portion which is hidden b y th e shadow of the fibre. The m ovem ents of th e fibre, however, are in a direction parallel to the length of the cylindrical prism , and as th e instantaneous position of th e fibre is indicated by an unexposed spot, a continuous record of these vibrations is formed on th e m oving film, which is carried on a revolving drum (see Fig. 5). The period of revolution of this drum is approxim ately 5 | seconds, and its speed is governed by an autom atic electric damping device. As th e drum is brought to rest after one revolution, th e record in each case is restricted to a period of 5 A seconds.

The magnification of th e combined vibro- m eter-cardiograph system is extrem ely high, and throughout th e tests it was never possible to employ more th a n one-third of the m axim um sensitivity for which the instrum ent is calibrated. G reater sensitivity even th an th is is available if required. This wide range of sensitivity th a t is im m ediately available and readily controlled by the electro-cardiograph is an im p o rta n t feature of great practical utility , as the instrum ent can be adjusted to the greatest sensitivity

practicable a t any p articu lar tim e. F u rth e r­

more, th e electro-cardiograph, being cali­

b rated im m ediately before each observation, furnishes a perm anent record of th e sensi­

tiv ity (in m illim etres per m illivolt) for each record.

The record (see Fig. 6) is crossed a t right angles to its direction of m otion by a series of parallel lines, which are produced by in terru p tin g th e focussed beam of light at regular intervals by m eans of a revolving wheel, F in Fig. 4, carrying one or more projections so th a t m om entarily no light falls on the film as these tra v e l p ast the slit,

F i g . 3 . — D i a g r a m m a t i c s k e t c h s h o w i n g a r r a n g e ­ m e n t O F C O IL I N T H E M A G N E T IC F I E L D , A N D T H E M E T H O D O F O P E R A T IO N B Y A N I N C L IN E D L I N K .

and in consequence a sharp line appears on the record. These lines indicate fifths of a second and form th e tim e scale.

A light vertical pointer situ ated im ­ m ediately in front of the cylindrical lens of th e electro-cardiograph causes a shadow to be throw n on th e him which is recorded as a line, a t rig h t angles to th e tim ing lines.

This pointer m ay be m oved a short distance horizontally by m eans of a sm all electro­

m agnet, th u s causing a discontinuity in the line w hich is produced on th e record. If therefore th is electro-m agnet is included in an electric circuit w hich is broken a t the m om ent of th e explosion, th a t in sta n t will be recorded on th e him by a discontinuity in th e otherwise continuous horizontal line.

H and Generator.—The charges were de­

to n ated by m eans of a hand generator,

specially modified for these tests by Messrs.

204 T H E M IN IN G MAGAZINE E vershed and Vignoles of Chiswick, who

kindly lent th e in stru m en t for th e survey.

This in stru m en t is capable of generating sufficient cu rren t a t 50 volts to detonate readily th e ordinary high tension electric d eto n ato rs th a t were em ployed th ro u g h o u t th e test. T his h an d generator proved a very convenient an d efficient m eans of exploding th e charges.

Explosives and Detonators.—N obel’s

“ A rctic G elignite,” which is generally regarded as th e sta n d a rd explosive, was em ployed thro u g h o u t th e tests, th e cartridges used weighing on th e average 0-1 lb. each.

The d eto n ato rs as already described were of the high tension electric type, in which the ignition is effected by th e passage of the electric cu rren t through th e flashing m ix tu re itself.

Locating th e traverse lines, shot points, and general surveying duties.

Assistants : L aying th e land lines, from

charge to seism ograph, an d from charge to h an d generator, digging holes for charges and refilling them , and o perating the hand generator.

Pr o c e d u r e.

—Owing to th e particular

characteristics of th e area, certain unusual difficulties were encountered w hich would not ordinarily be present, and these necessitated a m odification of th e usual procedure. It is the general p ractice w hen conducting a seismic survey, to arrange th e seismographs (usually from 3 to 6 in num ber) a t different distances from th e shot p o int, and after recording one shot, to m ove th e instrum ents to different locations, still shooting from the same position. T heoretically, in shooting a

Fi g. 4 . — Op t i c a l a r r a n g e m e n t o f p o r t a b l e c a r d i o g r a p h.

Leads.—V arious lengths, ranging from

150 ft. to 500 ft. of well insulated wire were em ployed. T he longer lengths were of well in su lated 3 (0-029) stra n d ed steel cable, b u t th e shorter lengths were of well insulated 0-029 tw in copper wire.

Stop-W atches.—Two sim ilar stop-w atches

were kindly supplied by th e D irector of th e M eteorological Office, a n d these g reatly assisted th e tim ing arrangem ent.

Pe r s o n n e l.

—T h e personnel consisted of

th e a u th o r, Mr. D. S. M etcalfe (the Com­

p a n y ’s G eophysical Surveyor) and two assistants. The various duties connected w ith th e survey were allocated as follows :—

The Author : In charge of th e seism ograph,

explosive a n d detonators, and also th e p rep a ratio n of th e charges.

M r. Metcalfe : Assisting in th e p rep aratio n

of th e charges. Responsible for laying th e charges, m aking th e necessary electrical connexions, and also th e firing of th e charges.

trav erse across an area, it is immaterial w hether th e seism ograph is m oved along and th e sh o t p o in t k e p t fixed, or w hether the seism ograph rem ains s ta tio n a ry and the shots fired a t various points along the profile, as is done b y R ieber. In th is p articu lar case it was found to be m ore convenient to adopt th e la tte r procedure. In th is w ay the routine w ork for each shot was reduced to a m inim um , it being necessary only to dig a hole to receive th e charge, prepare and lay th e charge, m ake th e necessary electrical connexions an d fill in th e hole. As th e whole of th is ro u tin e w ork w ould have been necessary in any case an d as only one seism ograph was available it was found more convenient to keep th e seismograph sta tio n a ry th ro u g h o u t each trav erse.

The seism ograph was set u p a t one end of the trav erse line w hich was th e n laid out and th e proposed sh o t p o in ts located b y pegs.

The two portions of th e seism ograph—the

A P R IL , 1930 205 vibrom eter, an d th e electro-cardiograph—-

were placed in separate h u ts ab o u t 60 ft.

apart, and connected electrically. The vibrometer was set up and adjusted, after which th e te n t was closed and left, and so was protected as m uch as possible from local disturbances. T he electro-cardiograph and the shot point were th en connected electric­

ally, and a sufficiently strong current passed through th is circuit to energize th e electro­

m agnet of th e explosion m arker on the electro-cardiograph. In th e longer shots a voltage of 16 to 18 volts was necessary for this purpose. A t th e shot point th is circuit was completed through a fuse wire either

say, j mile. The am ount of charge necessary, however, in any p articu lar case varies considerably w ith th e ty p e of ground, w ith th e distance, and also w ith th e am ount of ground unrest present a t th e tim e, th e la tte r controlling the sensitivity a t which the receiving and recording equipm ent m ay be satisfactorily operated. W ith th e charges indicated above, th e effect of th e explosion was to produce a c rater in th e sand or shingle ab o u t 5 ft. in diam eter and approxim ately 4 ft. deep. Pebbles of varying sizes were throw n laterally to a distance of about 250 ft.

and v ertically upw ards to a height of approxim ately 400 ft. A photograph of one

Fi g. 5 . — Ca m b r i d g e Po r t a b l e El e c t r o- Ca r d i o g r a p h.

threaded through, or wound round th e explosive charge (see Fig. 7) th u s ensuring th a t the circuit was broken a t the in stan t of explosion.

Ch a r g e s Em p l o y e d.—

The m axim um

charge employed during the survey was 12 sticks of Arctic Gelignite, b u t only in excep­

tional cases did th e num ber exceed eight.

W ith this charge it was found th a t over short distances, even in th e presence of consider­

able ground unrest, th e first arrival was readily determ ined. As th e distance increased, however, and approached 2,000 ft., the first arrival did not show up so readily, and it became m ore difficult to recognize th e arrival of th e first wave. There is little doubt therefore th a t larger charges should have been employed over distances greater th an ,

of th e explosions resulting from th e firing of 0-8 lb. of gelignite is shown in Fig. 8.

Pr e p a r i n g t h e Ch a r g e.

—The charge was

prepared by taking one of th e cartridges,

opening up th e paper w rapping a t one end,

and th ru stin g a pointed wooden rod into the

end of th e explosive, th u s m aking a cavity

in to which the deto n ato r was pushed and

com pletely buried. The paper cover was

th en replaced and bound firmly w ith twine,

after which this end was well covered w ith

tallow. The requisite num ber of gelignite

sticks were arranged around th e prim er

cartridge as centre, and th e whole securely

bound together w ith cord. A length of fuse

wire was th en th read ed through or wound

around th e charge and connected to th e two

wires leading from the sm all electro-m agnet