"rCilSTEi MILL
99The FlPSt Steamer built on the Clyde un the Isherwood System and classed 100 AS < Lloyd's.
B U I L T E Y
l
T H E LONGITUDINALLY FRAMED STEAMSHIP
CRA5TER HALL.
T H E system of ship construofcion prominenlly brought before the shipbuilding world i n April of last year through the paper read by Mr. J. W . Isher-wood, Middlesbrough, before the Institution of Naval Architects, and then subjectied to keen dis-cussion, has since been taken clean out of . the domain of theory and experiment and set firmly in
Craster Hall, built on this system, but with modifi-cations in detail, by Messrs. W m . Hamilton and Co., Port Glasgow, who have taken up the system under licence of the inventor. Mr. Isherwóod him-self, judging from his attitude and words in replying to the criticism on his Institution paper, does not claim to be in any absolute way a pioneer in the
F i g . 1—LAUNCH O F T H E O R A S T E R H A L L
place in the realm of praotiice. Although one vessel—the Paul Paix, an oil carrier—at that time being built at Middlesbrough has been afloat and i n service for a considerable period, and two others— for general cargo purposes—have been launched, and four more are under construction or on order, enterprising builders on the Clyde, as well as on the North-East Coast districts, are now earning a share of the credit attaching to sample ships built on the " Isherwood " system, and the immediate occasion of the present article is the launch, recently, of the
matter of the longitudinal principle of arranging the framework of ships. At the outset of his paper he refers to the fact of several vessels having been built by Soott Eussell in the sixties, i n which longi-tudinal framing was the outstanding feature, the Great Eastern, built on the "box unit system," being the most notable example. I f , as was alleged, he dismissed rather summarily what had been accomplished before in the direction of longitudinal construction, this was amply rectified i n the written contribution to the discussion by Dr. J. H . Bruhu,
who described and illustrated not only the Baron Osy, and others of Scott Eussell's productions, but gave particulars regarding vessels subsequently built by others—including J. B . Scott i n 1876 and in 1877—and called attention to methods of longi-tudinal framing he himself had proposed in papers read in 1897 before the Graduate Section of the Institution of Engineers and Shipbuilders in Scot-land, and on February 1st, 1906, before the Glasgow University Engineering Society, while, as Dr. Bruhn declared, he was still unaware that M r . Isherwood was working in this field. The latter, in the course
adoption in practice, and that methods of longitu-dinally framing vessels have been submitted to other institutions than the Naval Architects. One of these was dealt with in a paper by Mr. James Hamilton, M.I.N.A., entitled " A System of Ship-building, combining Transverse and Longitudinal Eraming," read before the Institution of Engineers and Shipbuilders i n Scotland on January 26th, 1875. The proposal described and illustrated by Mr. Hamilton involved the retention of the usual transverse system of framing on the bottom of vessels, with longitudinal framing arranged on the
Fig. 2—IVIIDSHIP S E C T I O N O F I H E C R A S T E R H A L L
of his reply, stated that there was no novelty in recent years simply in the fitting of longitudinal frames, or longitudinal beams, i n vessels. Several had been built w i t h longitudinal frames, and two or three with longitudinal beams also, but the reasons why the system had not been commonly adopted were that in these designs clear provision had not been made for the requisite transverse strength in vessels of whatever dimensions, nor for the recog-nised difficulties in the erection of such structures.
I t may here be stated, as affording additional evidence, that the subject has at intervals received attention from designers, though little definite
sides, but with transverse frames fitted inside the longitudinal framing, close enough to carry all the beams, and resembled generally the proposal by Mr. J. B. Scott in his paper read in 1871-2 session of the saane institution. Another proposal sub-mitted was that by Mr. Johan Johnson to the Norbh-Eist Coast Institution of Engineers and Shipbuilders on November 23rd, 1888. The title ot this paper was " A New System of Shipbuilding to Eaoilitate the Application of Machine Eiveting to Shell Plating," and i t was distinguished by much interesting.and sensible comment on the "longi-tudinal system of shipbuilding," and of Mr. Scott
O
feussell's advocacy and labours on its behalf. The system proposed by Mr. Johnson had features not unlike the other proposals already referred to. I t was put forward less on account of the need for additional longitudinal strength than to provide a system which would readily lend itself to the enlist-ing of mechanical aids in the way of layenlist-ing-off, erecting, riveting, &o. The side elevation and transverse section of a longitudinal method of framing vessels, devised by the author, i n collabo-ration with M r . Nicol S. Arthur, the inventor of the well-known frame-bevelling machine, were shown in the paper. This was the outcome of an idea which originated with them some years before while engaged in shipbuilding in Scotland. I n the-course of the discussion on this paper, quite a number of the principal shipbuilding firms on the North-Bast Coast spoke with warm approval of the proposed system, and in the case of one speaker— Mr. Eobert Thompson, of J. L . Thompson and Sons—the only reason for not at once adopting the proposal in practice was the attitude of Lloyd's Classification Society, before which designs and calculations bad been laid. Burther, in this con-nection mention may be niade of the ideas on the longitudinal framing conveyed in the course of an article on " Shipbuilding on the Longitudinal Blanged Girder System," as carried out i n practice by Messrs. Groom and Arthur, Leith, as pubhshed in T H E E N G I N B B E of April 27th, 1 8 9 4 .
The designation "longitudinal," however, is deprecated by Mr. Isherwood as regards the system associated with his name. I t is more correct, he says, to look upon i t as a " system of framing which readily admits- of longitudinal frames and beams advantageously forming part of the hull structure," and by means of. which, as is now amply proved, " the difiiculties have been overcome of building vessels with efficient and direct longitu-dinal stiffening as readily and economically as vessels built on the transverse system."
The adoption in actual practice of a general mode of construction based upon a system of longitudinal framing—even had such been adequately wedded to an efficient system óf transverse strengthening—has been retarded by a variety of causes. Eegard for the conventional and well-understood, and the general reluctance to adopt radical change i n structural methods, as well as the fear of increased cost entailed by suspected difficulties and lessened celerity of construction, have aU been retarding influences. Without doubt, these have been added to, and aggravated by, the conservative attitude of
the ship classification societies i n the face of proposed radical change, resulting in discourage-ment and difficulty for both the shipowner and the shipbuilder.
But for the obstacles referred to, structural arrangements, i n which longitudinal framing was a feature, would long ago have been better known in shipbuilding practice. Of late years, however, more readiness has been evinced—because, more suasion of a potent character has been brought into play—by Lloyd's and other classification bodies to consider and countenance changes of a radical nature. Hard times and economical conditions have influenced shipowners and shipbuilders alike -to devise new types and modify old methods, w i t h the result that "turret," " t r u n k , " and self-trimming steamers, and cantilever-framed, C-framed, and longitadinally-framed vessels are now much i n evidence, having the desiredolassifloation credentials. I t is not without its significance that the gentlemen responsible for the latest, and in some respects the greatest, departure from conventional lines in ship construction is one who has until recently and for a number of years been a prominent member of the surveying stafl" of Lloyd's Eegister. I t may well be supposed that his experience and intimate knowledge of the points of view f r o m which classifi-cation bodies regard innovations have helped him, if not to devise the system bearing his name, at least to pilot i t safely into the haven of official recognition and acceptance, B u t beyond, and pro-bably of more consequence than this, vessels built on the system have been shown to possess features and qualities appealing to shipowners even more strongly than to shipbuilders, and this has smoothed the way for readier and more general acceptance.
Into the question of the süperior strength . claimed for vessels built on the Isherwood system,
and the reductions i n weight of material which i t justifies, i t is not necessary at this time to go minutely. The evidence and arguments on this aspect of the subject are sufficiently dealt w i t h i n Mr. Isherwood's Institution paper of last year, as found, w i t h the discussion on i t , in the volume of " Transactions," or i n the abbreviated account of the proceedings published in our issue for April 17th, 1908.
-Briefly stated, the salient features of the Isher-wood system consist in associating with wide spaced transverse plate frames, which form con-tinuous transverse girders round the whole circum-ference of the vessel, longitudinal framing on bottom and sides, and longitudinal beams under
deck; the frames and beams bemg carried continuously from transverse bulkhead to trans-verse bulkhead. The transtrans-verse girders are, of course, notched on their outer edges to permit of this longitudinal continuity, a feature well brought out by the illustrations on our two-page Supplement. Each transverse girder embodies the function of a very strong frame, beam, and floor, and—important to note—is directly attached to the shell plating and deck. This is a vital feature i n the Isherwood system, and is most important, as it enables the shell plating to be considered as part of the transverse girder and a factor in the inertia of
to safer and easier transition inom the ordinary id the new system of construction. Eor example, each of the numerous transverse bulkheads required naturally lent itself as a transverse girder.
I n . the case of the Oraster Hall, to which our references will now more particularly be made, such incidenlal aid to facility of transition has not been so much a factor. Her holds, iptended for general cargo carrying, are much larger—72ft. long in one case—and the question of adequate trans-verse and longitudinal strength entailed greater consideration and care in arranging, if not i n actual construction. Again, the Oraster Hall is the first
F i g . 3 — K E E L P L A T E , C E N T R A L G I R D E R , A N D F I R S T L O N G I T U D I N A L
the frame girder. The same thing is true of the longitudinals, which are also directly attached tc the shell plating. "Where the longitudinal frames abut against the transverse bulkheads they meet the bulkhead stiffening bars, which are arranged at corresponding heighls, and are bracketed thereto, thus forming an unbroken framework bounded i n the athwartship direction by the bulkheads, and longitudinally by the ship's shell plating. I n the pioneer vessel of this system—the Paul Paix—the exigencies of oil-carrying arrangements i n the way of more frequent bulkhead divisions especially, longitudinal as well as transverse, lent themselves
vessel of this type tp be built for general cargo purposes to Lloyd's classification, and under their special survey, and i t is only stating a fact to remark that this of itself entailed the provision of extra structural details, and to some extent of heavier scantling, than other classification societies have accepted i n almost similar cases.
The Oraster Hall, which has been built on the Isherwood system, by-WilHam Hamilton and Oo., Limited, Port Glasgow, to the order of Oharles G. Dunn and Oo., Liverpool, after a close study on the part of the latter and their advisers, is a screw steamer having two decks and a poop, bridge and
foi'eoastle, her tonnage gross register being 4319 tons, and net register 2759 tons. Her principal dimensions are :—Length, 392ft. 6in. ; breadth, 50ft. ; and depth, 29ft. She has a dead weight capacity of 7300 tons, of which, it may at once be stated, as much as 250 tons are due to the'system of construction. A l l the latest arrangements for the rapid handling of heavy cargoes have been introduced, and the vessel is throughout lighted with electricity. Triple-expansion engines and other propulsive machinery have been fitted by David Rowan and Oo,, Glasgow.
K g . 1 is reproduced from a photograph of the vessel
the ship, the f LTII depth of the double bottom, which are intercostal with regard to the floor-plates coincident with the transverse girders, and to the intermediate floor-plates which divide the 12ft. spacing of the latter. Throughout the engine and boiler space, and in No. 1 hold, forward of the midship three-fifths length, the floors in double bottom are spaced only 4ft, apart.
Elsewhere throughout the double bottom, and in various structural details—such as vertical stiffen-ing angle bars on all floor-plates connectstiffen-ing longi-tudinal frames and inner bottom—liberal provision has been made for local strength w i t h the view of
Fig. 4 —C E L L U L A R D O U B L E BOTTOIVl, A F T J ^ E N D
taken when leaving the waysonEebruary 4th. Erom the midship section herewith—Eig. 2—and from several engravings given on page 242, and in our two-page Supplement, i t w i l l be seen that the Oraster Hall has a structural cellular double bottom. This is 3ft. 9in. deep at the cen<-re, and extends throughout the vessel. The transverse girder frames are spaced 12ft. apart, and the longitudinal bulb fratces 30in. apart, converging forward to 20in. apart. The longitudinal deck beams are 39in, apart throughout. I t will be seen that i n addition to the continuous centi'e plate girder there are three sister keelson longitudinals on each side of
meeting the owners ideas as to what is requisite in docking or in the event of grounding, and generally for the particular trade the vessel is to be engaged in. This, for the most part, is i n excess of the requirements of Lloyd's classification authorities. Eorward of the three-fifths length the spacing of the longitudinal frames is gradually reduced from 30in to 20in. apart. The main object in view ia to provide fully for the severe ordeal which cargo vessels are often subjected to in crossing the North Atlantic. The longitudinal frames are carried right to the back of the stem, and are there connected together by breast-hook plates. Other features
introduced to contribute to the strength of the vessel about the bow and forefoot will be gathered from our illustrations. Attention may here be drawn to the eiïeotive way in which the longitudinal framing contributes to strength in the event of bow-on collision, and to minimising the effect of broadside impact from the stem of another vessel. No such severe rupture can follow in the longi-tudinally-framed ship as i n the case of a ship with ordinary transverse framing, where the impact probably would take place between frames. The damage requiring repair in the
longitudinally-central girder—the notching for which may be seen in Fig. 3, page 242—thus affording additional and effective binding of the two sides of the ship, The transverse girders are stiffened on their inner edge by a single bulb angle 9in. by 3iin. by iUa., and are ccnneoted to the shell plating and to the deck plating by a single angle, öin. by 5in. by ^oin., double riveted, the latter, of course, being inter-costal with regard to the longitudinal frames. Where the latter pass through the notches i n the girders they are attached to the girders by angle lugs riveted to both members, every alternate lug
Fig. 5 - G E N E R A L VIEV^ O F
framed ship is likely to be much less, and the ease of repair greater.
The transverse girders, w i t h their combined edge stiffening of single bulb angle, are continuous down sides and across decks, but they are intercostal with regard to the wing-plate of the double bottom, which in the case of the Craster Hall is continuous. The corresponding floor plates i n the double bottom, which is 3ft. 9in. deep, are, of course, intercostal with regard to the continuous central plate girder, to which they are connected by double öin. by 5in. by -wu angles. The reverse frames on top of the floors have a connecting piece carried through the
C E L L U L A R D O U B L E ' B O T T O M
below the main deck, and throughout thé holds, being the f u l l width of the transverse girder frames, thus stiffening the latter and obviating any chance' of their tripping. The necessity of having these direct attachments of the longitudinal frames to the transverse girders has been questioned. ' Th'ë direct' attachment of both systems of framing to the shell plating, as has already been pointed out, is one o f the most vital features in the Isherwood system, and i t is urged, not without reason, that tlie shell • plating itself provides a gusset, binding the two parts of the structure efficiently together, when the riveting itself is thoroughly done, I n the case of
the Oraster Hall i t was found that i n addition to the strength afforded, the fitting of the lugs to girders considerably facilitated the construction. The lugs, which were attached to the girders before being brought to the berth, were used to secure the longitudinal frames as soon as erected, thus provid-ing convenient means of fairprovid-ing and bindprovid-ing,
Referring to. the longitudinal section and the shell-expansion plan on our two-page Supplement, it will be seen that sheer is given to the vessel as is usual in most ordinary modern ships, and that the longitudinal frames follow lines parallel
through-these, where found to be most expedient, before reaching the vessel's extremities. I n the case of the Oraster' Hall, with- the longitudinals running parallel to the sheer landings, extra longitudinals at the extremities were only required in the region of the bilges, outside the double bottom. W i t h the longitudinals running parallel to the shell landings the awkwardness in good fitting which might obviously be entailed by the line of direction of the longitudinals crossing the line of the shell landing was entirely obviated. B y this arrangement, the longitudinals were found to take the natural set^—
Fig. 6 - F O R W A R D END P A R T I A L L Y . P L A T E D
out to the deck sheer and shell landings. I n this respect the structure of the vessel is different from that of the first of the Isherwood vessels built at Middlesbrough, in which the longitudinals were fitted horizontally and parallel to the base line over the greater part of the vessel's length. Again, i n the Middlesbrough steamer, immediately under the deck at the ends, where the sheer rises more rapidly, additional longitudinals had to be introduced; while lower down, in the neighbour-hood of the bilges, the fining-off the ends com-pelled the longitudinals to converge, and, conse-quently, [it was necessary to terminate some of
normal to the inside surface of the shell—with ease, and without any machine bevelling whatever, while i n no case did a longicudinal frame cross a shell landing. Here i t may be stated that practi-cally the only filling slips required i n the Oraster
Hair
were those at the shell laps. Not only were all frame and beam slips dispensed with,'but the system of joggling was followed wherever possible, thus bringing the surfaces together without the intervention of filling pieces.Ooming to speak of the order and work of actuail erection, i t may be stated that in past systems, having longitudinal framing as a feature, the
diffi-culty of securing such frames in place, and i n fair-ing up, militated greatly against their adoption. I n the system under notice, as may already have been gathered, these difficulties are obviated or i n many
simplify and facilitate the fitting of the longitudinals, the latter simply being lifted into, the slots i n the transverses. The contour of the hull framing is thus as naturally evolved as i n the case of wood
T H E FRAMING BOW E N D L O O K I N G F O R W A R D
ways overcome. The widely spaced transverse girders, which are prepared for erection on the scrive board as in the case of transverse bulkheads, are readily set up at their stations, and greatly
boat building, where the planking is fitted close up to transverse moulds at wide intervals. The pro-vision of the transverse girders i n the Isherwood system enables the structm-e to be as economically
system, and surmounts the difficulties that have prevented longitudinal framing from sooner coming into vogue. A clear grasp of the combined
frame-aft peak bulkhead, the sharp and complex curvature of the ' run " and " counter " at that part making the adoption of the ordinary transverse system more
L O N G I T U D I N A L AND T R A N S V E R S E V^EB F R A M I N G L O O K I N G A F T
work, as regards both sides and decks, and of the manner of erection, can be got from the sectional view on our two-page Supplement. From the longitudinal elevation on the same plate i t will be
convenient. At the bow of the vessel the com-paratively plain bevel of the sides or " entrance " permits the continuation of the longitudinal framing right to the back ot the stem, and, as has already
lo
been pointed out, this fact of longitudinal framing forward of the peak bulkhead renders the vessel greatly more impervious to the shock and damage usually resulting from stem-oh collision. As before stated, also, the longitudinals, although curved to the " line of entrance," did not reguire any bevelling as regards their vertical or horizontal flanges.The erection of the transverse girders involved only a straight run of work from stern to stem, the bulkheads, as before stated, being treated aa involv-.ing the function of a transverse girder for erection
purposes, and by the time one-third of the vessel's length.had been fitted w i t h the transverse frames, the fitting i n of the longitudinal frames and deck beams was already under way. Erection, in their case also, meant only a straight run of work. The brackets for attachment of the longitudinal frames to the transverse bulkheads were hydraulically riveted to the longitudinals before these were lifted into place, and the lugs upon the transverse girders were also hydraulically riveted before being taken to the building berth. I t will thus be seen that as erection advanced the work was ready for riveting up, all the framing being i n position. The way i n which the lugs on the girders contributed to ready fastening of the longitudinal frames, and to fairing of the structure, has already'been referred to. A l l that was necessary in the matter of ribands for general fairing was one stout riband at the gunwale for securing the transverse girders. Practically •nO fairing was required other than that which,
the longitudinals themselves afforded, i n eon-.junotion w i t h the girder lugs, as already . explained. • . Nearly the whole of • the framing of the Craster Hall was made to templates, and no trouble was i n any way experienced either through misfit of the structural parts or through prejudice on the part of the workman to necessary modifications in methods of work entailed by the new system, The system lends i t s e l f ^ a t leeist i n Messrs, Hamilton and Oo.'s experience^to a larger number of workmen being employed in the earher stages of progress, and to a better division of labour than obtains in ordinary practice. Eor example, -instead of the frame setting being deputed and. restricted to the members of one squad of regular frame-setters, the work was spread amongst four or five squads of workmen, mostly belonging to the branch known as " keelson fitters." I n this way, and on account of the fact that no bevelling whatever of the longitudinal framing was required, the ' rate of progress i n the earher stages of construction was not measured by the capacity of the frame-heating furnaces, or the
productiveness of one sqviad of frame-setters. The transverse girders were dealt with by the bulkhead squad, all these, as well as the wing plates of the transverse bulkheads, being prepared from moulds or templates, taken from the loft floor, thus greatly facihtating progress in erection.
Advantages, incidental as well as inherent i n character, can be pointed to as pertaining to the Isherwood system, not alone as regards the pre-liminary stages of design, but in respect of a ship's after-life in service. I t affords, for example, more elasticity than in the ordinary system of construc-tion i n the matter of fixing the posiconstruc-tion of the hold bulkheads, cargo hatches, and other structural fea-tures and working arrangements, according to the exigencies of particular-services or kinds of cargo to .'be carried. Thus, instead of being a multiple of the frame spacing, as i n transverse framed vessels, the - biükheads can be fixed the precise distance •apart to suit circumstances, and precisely in the
most suitable position relative to other features. This enables the transverse girders to be spaced equi-distantly between the two bulkheads, on the principle, i f thought advisable, of providing for the compact stowage of- measurement goods. Thus, for example, .case oil, cotton bales, quarters of dead meat, and such other common, items of measurement cargoes, cap be better provided for. I n passing, i t may here be pointed out that , a gain in measurement capacity is secured . by the system under notice. There is more stowage space on the hold floor at the round of the bilge, Owing to the absence of bracket plates there, and. under the deck at the side, owing to the absence of the beam knees obtaining in the case of ordi-. nary transverse framed vesselsordi-. Messrsordi-. Hamilton - a n d Co, estimate the total increase i n cubic
capa-city for bale or case goods i n the holds of the Craster H a l l at nearly 2;per cent.
I n many directions the system under notice, and i n the experience of Messrs. Hamilton and Co., lends itself incidentally to improved workmanship. Not the least important of these directions is con-cerned w i t h the preparation of the rivet holes and the riveting. The extent to which the templating system can be followed, and the more accurate fitting this admits of, has already been referred to. This, of course, results in more accurate punching of holes i n items to be assembled—one item relatively to the other. But another factor contributing to this result, i n Messrs. Hamilton's experience, con-sists i n the fact that, most of the hole punching being i n the direction of the length of structural
items, there is a straighter run and easier manipu- relatively to the machine, a cross operation i n lation of the item through the punching machine. which the men handling the plate are apt to be at There is more continuity i n the run of operations " cioss purposes."
than i n much of the punching required under the As some evidence of the accuracy characterising
I N T E R I O R O F H O L D A S C O M P L E T E D
ordinary system of construction—for example, the the work of punching and fitting i n this ship, i t punching i n the shell plating for every transverse was mentioned to our representative that i n the frame. This is, of course, across the plate, and is wages paid to hole-borers alone there was a very done by short out-and-in movement of the plate, substantial saving, as compared w i t h the
corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ corre-^ . . .
sponding item of labom- i n a sbip of the same size built i n the ordiuary way. Some proportion of this saving would be due to fewer holes having been left for the hole-borers to accomplish, which in itself speaks well for the system of templating and punching followed, and for the accessibility of structural features. One or two odd facts as to the advantages incidental to the longitudinal system may, i n a word, be referred to. During construc-tion the longitudinal framing naturally lent itself as
a sort of ladder or staging i n the work of construc-tion.
Thus rivets were thrown by the rivet boy on to the longitudinals, which acted as shelves and dispensed with the necessity for a "catch-boy." I n the painting of the interior the longitudinals were of service as natural scaffolding. The inside wood sparring i n the Oraster Hall, as will be seen from one of the engravings in the Supplement, was fitted vertically in removable sections, which in itself is a matter of great convenience i n the after-life of a vessel in connection with the facihty of over-haul, &c,
Throughout this article i t has not been convenient to group the manifold advantages in any systematic way, but a summary of the outstanding advantages
from a shipowning point of view may be given i n closing.
While affording at least equal transverse strength to that obtained in ordinary practice, the Isherwood system yields practically 20 per cent, increase i n longitudinal strength, and permits of the work being produced without any increase i n cost. The redistribution of the inaterials used i n giving effect to the principle has enabled Messrs. Hamilton and Co. to reduce the weight of steel i n the structure, and also to dispense with the cement chocks usually fitted at the top of the close ceihng and at the sides of 'tween decks, with the result that in the case of the Oraster Hall the deadweight carrying capability is increased by at least 3 i per cent, as compared with a vessel of the same model, draught and coefficient built on the ordinary system. The ratio of deadweight capability i n the Oraster H a l l to the net registered tonnage is 2,64, as against 2.55 i n the vessel of ordinary construction. When i t is recognised that this extra earning power is- obtained without additional first cost, and with-out interfering in_ any way w i t h the steaming qualities of vessels, shipowners are perforce led to a serious consideration of the Isherwood longi-tudinal system of construction.
