350 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[October, 



^ilate, about 7 feet abaft the fore-foot, but tlierc it only occnsioned a sligbt. 

 though long indentaticn. The principal damage was on the starboard side 

 under the bilpe, and at the station of the foremost bulkhead. The (utside 

 plate or jilanking was cut ihrovifih by the blow having forced it on to the 

 ed<;es of the bulkhead plates ; and the lower plate of tjjC Inilkliead was broken 

 l)y this pressure. Tlie wooden sleeper, which lay on the iron floor almost 

 diiecily above the blow, was started up li inches from off the floor, and tlie 

 iron bolt which secured il to the Hoor was broken. 



The blow, to liave produced such damage as has been described, must evi- 

 dently have been very severe. It apparently clearly establishes that tlie in- 

 jury afiects the part struck only, for the rivets seem to have held as tif;ht, 

 and the contiguity of the plates of iron to have remained as perfect after the 

 tlow as before it had occurred, excepling onlv the plates cut by the bulk- 

 lead. There might have been a very rational 'doubt, before the experience 

 this accident has aff rded, whether, under such an injury, sheets of iron 

 would not have rent almost as sheels of paper would teal ; and whether the 

 livets would not have started by the dozen at a time, as the stitches in the 

 seams of a sail. Several of the plates aba^t the cut plates were indented in 

 a long wa\7 indentation. The greatest depth of the indentation occurred at 

 the cut, where it was 31 inches. 



The injuries were repaired by placing a shoe over the fore-foot, somewhat 

 similar in shape to the shoe used to drag the wheel of a carriage when going 

 down hill. This shoe was riveted strongly, by rivets passing through it and 

 tlie gripe, from side to side. The two plates of the bottom which were cut, 

 and the plate of the bulkhead which was broken, were taken out bv punching 

 out the rivets, and new plates were substituted for them. Those plates which 

 ■H-ere only inden'ed were taken out, straightened in the fire, and replaced. A 

 small quantity of the angle iron framing, ccnnccting the bulkhead to the bot- 

 tom, was also removed, and substituted by new. According to information 

 afforded by Mr. I^aird, the weight of new materials used in the repairs was 

 under 3 cwt. and the e.xpense for tlie materials, and wages of the smiths and 

 riveters, about £30 ; which, he says, would have been diminished to £20, if 

 lie could have had the facilities that are afforded by his own factory. 



It is not ea^y to institute any comparison between the expense of this re- 

 pair and that of a similar accident to a timber-built ship, because we cannot 

 ascertain what would have been tlie extent of the damage. If any timbers 

 had been broken, which would in all probability have been the case, the ex- 

 pense would h.ave been much greater. But unless timbers had been broken. 

 the mere upsetting of the gripe of a ship, the rubbing off' of a few sheets of 

 copper, and the shifting of a plank or tw o, would no! have involved expense 

 much exceeding that of the repair of the Nemesis. 



Before the vessel was grounded upon the blocks, sights were placed towards 

 each extremity, 140 feet apart, with a third sight between them. By means 

 of these sights, observations were taken before and after groun-ling, and the 

 deviation from the straight line, in the length of 140 feet, was only a quarter 

 i)f an inch. 



Two questions now naturally arise : — 1. What are the adv.-,ntages or dis- 

 advai ;agcs of the iubstituticn of iron for timber in the ccnstniction of ships P 

 — 2. To what limit may this substitution be advantageously carried? Among 

 the advantages are the employment of a less material, of whicli the supply 

 is inexhaustible, and for which supply we are totally independent of other 

 -nations. Also, the greater durability of the m lerial, not only arising from 

 its relative durability with that of timber, but from its requiring no metallic 

 sheathing to protect it from the ravages of worms. Also, the greater dura- 

 bility of the structure as a whole, in consequence of the greater permanency 

 in the perfect combination of its several parts, arising fr^ m the fastenings 

 teing of the same hardness of texture as tlie portions of maieiials brought 

 into connection. The metallic astenin:;s to a timber-built vessel act. it must 

 be remembered, not only chemically but also mechanically, to accelerate her 

 flertruetion, immediately the clore connection of the several parts is at all 

 fliriinisbed. 



'These appear to be the principal advantages of iron in connection with the 

 qu 'Stion, as far as first expense of material and durability are concerned. 

 Bit these considerations are independent of the expense in relation to the 

 comparative total quantities of materials reiiuired to build a ship of each sort. 

 Fcr it must be remembered that the iron-built vessel is of iron alone: the 

 Jit iber-buill vessel is of timber, iron, ami copper. 



iVerc it possible to compare an iron-built ship with one entirely built of 

 limber, setting aside the question of durability, undoubtedly the advantage 

 -would be wholly on the side of the timber-built ship. For the strength of 

 oak is one-fifth that of wrought iron, and its weight is only one-eighth tliat 

 of wrought iron. But this comparison is untenable, because of the great 

 quantity of metal which necessarily enters in the construction of the tiinber- 

 built shp, by which its relative weight is very much increased, and its rela- 

 tive strength diminished. By the term "timber," in speaking of a timber- 

 built ship, a compound of timber, copper and iron is meant, having less 

 strength in proportion to weight than the timber alone, but greater weight 

 in proportion to strength. It is impossible within the limits of this paper to 

 investigate the actual weights of wood, iron, and copper, which enter into 

 the composition of a timber-built ship, in order to ascertain the exact answer 

 to the question as to which is the heavier material ii; proportion to its strength, 

 the "timber" of the timber-built ship, or the iron of the iron vessel. 'We 

 shall, however, assume as correct that which we believe would be found to l.c 

 ■so, viz. that the material of the timber -built ship would be the heavier in pro- 

 portion to its strength, and shall proceed to the further investigation of the 

 original questions on that assumption. Therefore, by the substitution of 

 iron we obtain equal strength wiih less weight of material. From which ad- 

 vantage it follows, that if the " limber" and the iron vessel be each built for 

 the same loaded displacement, the iron vessel, with equal strength will be 

 capable of carrying a heavier cargo, and with greater strength an equal cargo. 

 Also, that if a "timber" and an iron vessel be built of the same strength, 

 and to carry the same weight of cargo, the iron vessel may be of less dis- 

 placement, and consequently smaller in dimensions, or if of less displacement 

 with the same dimensions, may be more advantageously formed for velocity 



and for weatherly qualities. The small dimensions 'nvolvc the advantage of 

 light dr.aught of water, diminished expense, and l.ss numerous crew, xhe 

 diminished displ.acement with the small dimensions involves quicker return 

 of capital and greater safety in navigation. 



The answer to the second question, as to the limit in the size of the vessel 

 to which the substitution of iron for " timber " may be carried, appears also 

 to be in-.-olved in the foregoing considerations. For, if greater strength may- 

 be obtained with equal weight of material, or equal strength with less weight 

 of material, there can be no limit short of that limitation which may equally 

 apply to " timber.' And. by an application of the foregoing reasoning to the 

 question at issue, it appears that a first-rate may be more strongly built of 

 iron than of timber, with the same light displacement, and equally strong 

 built, but capable of carrying a greater quantity of water, provisions, and 

 stores, with the same load displacement; or. equally strongly built, and 

 capable of carrying an equal quantity of water, provisions and stores, with a 

 less load displacement. This may appear to be a bold and startling result of 

 our investigation : but if our original assumption be correct, it is nevcrtlie- 

 less. within the bounds of truth. Nay. it is even an under estimate of the 

 limit to the substitution of iron for wood in the construction of ships. For 

 the limit to the possibility of constructing a fabric of any conceivable dimen- 

 sions is necessarily dependent upon the ratio of the strength of the material 

 used to its weight. And as this is greater in iron than in the " timber" of 

 the timber-built ship, the limit of dimensions for the iron-b.iilt ship is more 

 extended than the limit of the dimensions of the timber-built ship. 



It may. perhaps, be necessary to repeat that the word "timber" in this 

 investigation means the copper, iron and wood of the timber-built ship. • 



If we take'into consideration the very few years that have passed since the 

 first application of iron as a total substitute for timber in building ships, it is 

 astonishing to what perfection this branch of art has arrived; and, conse- 

 quently, very great credit attaches to Mr. Laiid. tor the intelligence and 

 talent which he has displayed in thus adding to the manufacturing resources 

 of this country. As the art proceeds, and becomes more general, there can 

 be no doubt that great improvements will be made. This is said without the 

 slightest intention of withholding from Mr. Laird the high meed of praise 

 which is so justly his due. In speaking of the progress of improvement, we 

 are too prone virtually to set bounds to its advance ; forgetful of the fact that 

 perfection being unattainable by mortals, it is a mere abstract term, meaning 

 one thing yesterday, another to day. and another tomorrow. One improve- 

 ment, and that probably not an unimportant one. would be the diagonal 

 arrangement of the plates or planking of the vessel, and also of the angle 

 iron frames. Iron offers greater resistance to compression than to extension. 

 And bar-iron offers greater proportionate resistance to extension than plate- 

 iron. These facts, wHiich have been ascertained by experiment, enable us to 

 determine upon the positions in which to place the plates, so that the pecu- 

 liarities of strength of the angle and bar-iron shall be most advantageously 

 developed. The angle iron should be placed so as to act as tru ses in sup- 

 porting the weight of the extremities of the vess 1 ; the weight or dow nward 

 pressure of which is neces-arily greater than the upward pressure of the 

 water. The frames should, therefore, be placed with their heels toward the 

 midship part of the ship, and their heads inclining forward in the fore body, 

 and aft in the after body to an angle of 45 degrees with the horizon. The 

 plates have already been described as connected together at their edges by 

 being riveted to strips of bar-iron. These may form the ties, and the direc- 

 tion of these continuous bands should be at right angles to the direction of 

 the angle iron frames. Thus the whole'body would be divided by these two 

 series of lines into compartments ; which, in the vertical part of the body, 

 would be squares, each with one diameter vertical and the other horizontal, 

 as in the following sketch. Tlie double lines are the angle iron frames, the 

 single lines the continuous bais to which the edges of the sheets rre riveted. 

 Of course, the angle iron frames will receive the rivets of one series of seams, 

 and therefore by ibis adjustment some small weight of iron will be saved. 



The floors and all the lower part of the vessel may remain as in the Ne- 

 mesis. The introduction of water-tight bulkheads is very gooil. This has 

 been be''ore attempted in timber-built ships, but has failed, from the igno- 

 rance of (he pri jectors of the nature of the pressure of water. They assumed 

 that a caulked bulkliead of three or four inches in thickness, that would be 

 quite adequate to resist the pressure of a small depth of water, would also be 

 of su.fficient strength to resist the pressure to which it would be subjected by 

 •Iceper immersion. Bulkheads, to resist the pressure of water, must increase 

 in strength in proportion to their depth below the surface of the water. 

 This fact must not be lost sight of in the construction of these water-tight 

 iron bulkheads. It is not of consequeni c with small draughts of water ; but 

 when larger and deeper vessels arc built of iron, it will become a question of 

 importance ; and if not duly attended to, the kha of safely from water-tight 

 bulkheads may be most delusive. 



The question of the durability of these vessels, of their little liability to 

 accident, and of the ease with which damage done to them may be repaired, 

 appears to be very clearly proved from the experience w hich has already been 

 obtained on these points; and this is not little, for there are boats built by 

 Mr. Laird in both North and South America ; in all parts of India, and on 

 the Euphrates and the Indus ; in F.gypt, on the Nile and in the Mediterra- 

 nean ; oil the Vistula, on the Shannon, and on the Thames, One of these 

 boats on the Savannah has been constantly at work for these last six years 

 without any repair ; which is a great test, if we consider the frequent, con- 

 stant caulkings required to preserve a timber-built ship. There is also a 

 steam-yacht Iniilt of iron, the Glow-worm, the property of Asheton Smith, 

 Esq. This vessel has made the passage from Bristol to Carnarvon, a distance 

 of 210 miles, in 18 hours. In the report to the House ot Commons on steam- 

 vessel accidents, we find the following slated of the Garryowen, one of these 

 vessels : — " We went ashore about two cables' length to the eastward of the 

 pier (Kilrush) and struck very heavy for the first hour. The ground under 

 oilr weather-bilge was rather soft clay, covered with shingle and loose stones, 

 some of them pretty large. Under our inside, or lee-bilge, the ground was 

 very hard, being a footpath at low water. I was greatly afiiid slie would be 



