THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



256 



vessel to trade, and remunerate the owners, in cases in «l"ch a 

 wooden vessel would not return a profit ; for, if we suppose tliat the 

 freight of a 500-ton ship would just pay tlje expences required to 

 navigate her, an iron vessel would leave the freight on the extra 100 

 tons as clear profit." . , 



"An iron vessel required to carry 250 tons, therefore, equals, in the 

 first cost, a wooden vessel that will carry only 200 tons ; and an iron 

 vessel required to carry GOO tons will cost less than a wooden vessel 

 built to carry only 500 tons." 

 Again, of steamers he says, 



" The comparison is much more in favour of iron than with wooden 

 vessels. As the average cargo of a steamer is only, perhaps, about 

 one-third of the load, in engine, cargo and coals together, an increase 

 of one-fourth in her stowage adds 75 per cent, to her capacity for 

 carrying cargo. In other words, to carry a given cargo, the iron 

 steame?may be much less than a wooden one." 



Light draught gives the iron ship the monopoly of shallow rivers, 

 and cannot fail to lead to a great extension of navigation. The Indus, 

 chiefly on account of physical difficulties, has hitherto been a closed 

 river ; the employment of the new class of vessels must, therelore, 

 create a lar" e traffic on its waters. Cleanliness is a mercantile quality, 

 and is accompanied by health, the nuisances of bilge water and vermin 

 being got rid of in the iron ^hips. With regard to the latter annoy- 

 ance, it is related that a colony of rats took possession of the Iron 

 Duke previous to her first voyage, but not relishing the obdurate 

 material of which she was built, a portion of them deserted her at 

 Calcutta, and the remainder immediately on her return to England. 



StrenMh goes a great way to ensure safety in a vessel, and iron 

 plates in%trength are, to English oak, as 49-CS to 10-01, or nearly 5 to 1. 

 Iron ships are further to be preferred in this respect as readily ad- 

 mitting the division of the hull by bulkheads. Superior speed Mr. 

 Grantham claims as one of the results to be expected from the extended 

 use of iron. He considers that the cheapness and flexibility ot tliis 

 material will allow of the model of a vessel being made finer, without 

 corresponding loss in the amount of steerage, and m the carrying 

 qualities. In the event of accident, the repairs of iron ships are very 

 tritiing, as instanced in the case of the Nemesis war steamer, which 

 ran on one of the SciUy rocks in the British Channel with such violence 

 that, to use the expression of Captain Claxton, "if she had been of 

 wood she would most probably have left her bones on the spot." bhe 

 was however, navigated round to Plymouth, and the repairs easily 

 effected for about 3U/. On the subject of repairs the author so often 

 quoted declares that it is erroneous to assume that iron vessels are 

 more difficult to repair than those of timber, for the injuries are 

 generally external and confined to a single spot, and may in most cases 

 be sufficiently repaired by any ingenious man, if the ship be but pro- 

 vided with a" few drills, spare plates, bolts, and other necessary articles, 

 which no captain should neglect to carry among his stores. Besides, 

 he says, when iron vessels become more generally employed, the 

 necessary assistance will be found at all considerable ports and stations 

 at which" they may touch. We may add, too, that ultimately the ship's 

 blacksmith will be rated instead of the ship's carpenter, or perhaps 

 in Queen's ships the rating of the armourer raised, hi warfare the 

 resistance of the iron sheeting to the impact of shot striking the hull 

 in an oblique direction is an advantage, while even a shot entering the 

 vessel is less injurious than in timber ships, as no splinters are pro- 

 duced—the great cause of death and wounds. Shot holes in iron 

 sheeting adroit of being readily stopped, and in an easy manner. The 

 injury from the recoil of lieavy artillery, such as is now used, is less on 

 board an iron ship, and enables them to carry a heavier armament. 



It is to be regretted that, in their anxiety to secure contracts, iron 

 ship-builders have sometimes been tempted to construct vessels of a 

 less degree of strength than due consideration would have dictated, 

 and have thus endangered the success of the system. Plates of all 

 forms and dimensions have hitherto been used, from -f^ to | of an inch 

 in thickness, but Mr. Grantham observes that these are by no means 

 the limits within which the plates must of necessity be made ; some 

 of much greater strength will, in the farther progress of the art, most 

 probably be put in requisition. Of late, as the size of the vessels 

 has increased, and the extent of the voyages peformed by them, the 

 strergth of the plates has been increased. On strength of material 

 it is to be remaiUed, that oxidation proceeds no faster on the surface 

 of thick iih'.tes than of thin plates ; so that plates of i inch have 

 double llie durability of those only l inch in thickness. In his 

 remarks on jointing Mr. Grantham decides in favour of the lapped joint 

 in prelercnre to the fiusli joint, and also in favour of double rivetting. 

 By Mr. Eairbairn's tables read before the British Association at Glas- 

 gow, it appears that, assuming the strength of plates to resist tension 



[August, 



to be .. .. r. 100 



A double rivetted joint will be '^ 



And a single ri vetted joint , •• . 



In the system of fiush-jointing, twice the number of rivets are re- 

 quired : and, therefore, to obtain the advantage of double rivetting, 

 four rows of rivets are necessary to each joint.* As to the objection 

 which has been raised to the lapped joints, that they make the hull 

 rout'h and lessen the sailing powers, Mr. Grantham's defence is that it 

 is very questionable whether the edges, presented in almost straight 

 and parallel lines, can at all impede the vessel's velocity, while 

 they give her a better hold of the water. In reference to an inquiry 

 whether, in case the heads fly off and the rivets fall out, the strength 

 of the vessel is lessened, and a hole left for the admission of water, 

 our author observes that he never heard of such an accident, and that 

 in his yard no occasion has been found to replace a single rivet. 

 Should.'however, the head of a rivet break off while the vessel is 

 afloat, it by no means follows that the rivet itself should fall out ; on 

 the contrary, when originally secured in a workmanlike manner, the 

 piece remains so firm in the hole as to require the application of a 

 strong sledge to drive it out. Among the errors to be guarded against, 

 Mr. Grantham places that of bolting on a false keel of timber to an iron 

 vessel, by which the Iron Duke, a vessel of 3.50 tons was nearly lost, 

 for haviiin- struck heavily on a sandbank, she tore away the false keel, 

 and broke oft" the bolts by which it was fastened, so that the water 



entered the holes. , , •, , •,., 



Considered as a national question, and with regard to its capability 

 of extended application, the use of iron in ship-building acquires a 

 ereat importance. At present the shell merely is of iron, but the 

 decks and bulwarks must ultimately be made of that material. In the 

 shape of chain, iron has been extensively used for cables and for run- 

 nine rieeing, for halliards, topsail sheets, &e., in which latter capacity 

 it is found to be superior to hempen cordage as being much more 

 slender than ropes of the same strength, so that it will pass through 

 smaller sheaves or blocks, while it stands better to its work from not 

 being subject in atmospheric changes to any perceptible expansion or 

 contraction. The introduction of wire rope will, under such circum- 

 stances, evidently lead to a greater use of iron even for rigging. For 

 masts iron has also been adopted, and Mr. Grantham mentions one as 

 in use for upwards of twelve years in the Ballinasloe steamer, without 

 sustaining any perceptible loss in its strength. This mast serves also 

 as a ventilator to the cabin. As we stand now with regard to mate- 

 rials for shib-buildii.g and rigging, we are dependent on foreign coun- 

 tries, while our builders labour under great disadvantages in compe- 

 tition with their foreign rivals with regard to both timber and hemp, 

 the raw materials of their art. Little timber, be it remembered, is 

 grown in this country, where it is a precarious and little profitable 

 production, subject to the ravages of the worm and of fire, and requir- 

 ing many years before it brings a return. Neither does it give much 

 employment to labour in its production or subsequent application. 

 Mr. G'rantham, on this subject, remarks in a paper read before the 

 late meeting of the British Association at Manchester, that the H,n- 

 rfos/a» timber vessel had cost £72,000, of which about i 12,000 was 

 for labour, and £48,000 for wood, and much of this was expended in 

 the East Indies; but an iron ship of £72,000 value would cost£b/,000 

 in labour, all expended in this country, and the remainmg £o,000 

 would also be paid here for the raw material. Were iron substituted 

 for timber and hemp, we should not only give greater employment to 

 iabour in our mines, but also in our building yards and to our seamen, 

 for now the inducement is to build ships in those countries where the 

 material is most abundant, while we cannot compete in freight with 

 ships built by several other nations, owing principally to the compara- 

 tively low rate at which they can procure the materials for building. 



The steam navigation interest is that which has the most to look 

 forward to from the general introduction of iron. At the present day, 

 the machinery and fuel occupy so large a portion of the vessel, that 

 very little room is left for stoWage. The weight and tremour of the 

 engines shake and strain wooden vessels and the machinery itself, 

 until the repairs of both swallow up most of the profit which would 

 otherwise be realized. The necessity for a greater degree of adap- 

 tation between the vessel and the machinery, is a topic which Mr. 

 Grantham has well handled. The engineer, he complains, is generally 

 very vet^ardless of the requirements of the vessel, and the ship-builder 

 often clings to principles of construction, which, when applied to 

 steamers, are ill suited to the attainment of a high speed. A wooden 

 vessel, when she takes the ground, and frequently when she encounters 

 heavy weather, becomes so much altered in shape that, were the en- 

 gines so attached as to form part and parcel of the whole, they w ould 



" Vide also Mr. F.ilibairn on rivetiiiig boiler plates by machinery, at page 

 351 of our 3rd Vol. 



