322 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[October, 



ATMOSPHERIC AND ROPE TRACTION RAILWAYS. 



Mr. P. Barlow's Experiments cotiiparing the Power Lost. 



Tadle, sliowing a Comparison of the Useful Mechanical Effect of the Dalkey Engine, as applied hy the Atmospheric Pipe, with tliat of the 

 Tyler Hill Engine on the Canterbury and Whitstable Railway, as applied by the Rope. 



It will be seen by this Table that the loss of power by Rnpe traction varies from twenty to fifty-one per cent., and by Atmospheric traction 



seve.nty-six to eighty-five uer cent. 



THE GREAT BRITAIN. 



The Great Western Steam Ship Company originated with a few directors 

 and proprietors in the Great Western Railway Company, who entertained 

 the idea, that on the completion of the railway from London to Bristol, a 

 direct line of communication, hy means of steam-boats, to New York, as the 

 focal point of the New World, might be established with advantage. The 

 Great Western fulfilled the expectations entertained of her by her projectors, 

 in all respects, except in that, like many other moderate sized steam vessels, 

 so large a part was occupied by the machinery, relatively to that which could 

 be appropriated to passengers ami goods, the deficiency of space was soon 

 found to operate disadvantageously, in a pecuniary point of view. At first 

 it was intended that their second ship sbouhl be of tioiiier, but the superior 

 advantage which the introduction of iron appeared to hold out, induced a 

 very careful comparison, and an investigation into the state of some small 

 steam vessels already constructed of this material, and the result was the 

 abandonment of the previous resolution. As no example of an iron steam 

 ship of sufficient size existed, on which to base any calculation of the thick- 

 ness of the iron to be employed in its construction, or of the disposition of 

 the material, in order to olitain the greatest relative degree of strength ; 

 much consideration was lequisite, and it became necessary to organize an 

 establishment for building iron instead of wooden ships, before the keel of 

 the new vessel was laid. 



Dimensions, Tonnarje, &^-c. — The principal dimensions of the hull of the 

 Great Britain are, length of keel, 289 feet ; lengtli aloft, 322 feet ; main 

 breadth, 50 feet 6 inches ; depth of hold, 32 feet 6 inches. The tonnage, 

 according to the usual mode of builder's measurement, is therefore, 3,444 

 tons. The weight of iron used in the hull is about 1,040 tons: which is 

 equal to an average thickness of 2^ inches. The weight of wood-work in 

 the decks, fittings, &c., is about 370 tons. And the weight of the engines 

 and boilers (exclusive of the water) is 520 tons. The total weight, therefore, 

 is 1,930 tons ; which, at a draft of water of 10 feet 6 inches aft, corresponds 

 exactly with the calculation of the displacement of the hull, which is as 

 follows : — 



She will therefore be able to take 1,000 tons of coal, and 1,000 tons of 



measurement goods, weighing perhaps 400 tons, at a draft of 17 feet for- 

 ward, and 17 feet 6 inches aft. 



Keel. — The keel plate consists of plates iihs of an inch in thickness, by 

 20 inches wide, which are weldrd into lengths of 50 feet to 60 feet, and 

 these lengths are joined together, by very accurately made scarphs, 1 foot 

 6 inches in length, and riveted all over, at distances of 4J inches apart. The 

 end pieces of the keel, which are more liable to touch the ground, are full 

 1 inch in thickness. The stem is 12 inches deep at the forefoot, by 5 inches 

 thick, and at the 8 feet water mark, it is 16 inches by 2-5 inches; thence it 

 diminishes gradually to 12 inches by IJ inch. It is welded in one piece 18 

 feet long. 



Ribs. — The ribs or frame are formed principally of angle iron, 6 inches hy 

 3^ inches by |th inch, at distances of 18 inches from centre to centre, but 

 inclining gradually to 24 inches at the extremities, w'lere also angle iron, 

 6 inches by 2q- inches, and 4 inches by 3 inches, is used. In that part of 

 the body of the ship which is occupied by the engines, the ribs are doubled, 

 by having a similar angle iron riveted to them, with the web inside, or, as it 

 is termed, " reversed." 



Plalinj. — The outside plating commences with plates, 6 feet to 6 feet 6 

 iaches long, and 3 feet wide, by \^ inch thick ; of these plates there are four 

 courses ; these are followed by several courses of 5 inch thick, which is the 

 strength of the whole of the immersed part, up to the deep load water line. 

 Above that height the same thickness is preserved a-niiiNhips, but it is gra- 

 dually reduced to J inch thick quite high up, and at the extremities, with 

 a view to lighten them. 



Sleepers. — The longitudinal floor sleepers are ten in number; they are 

 3 feet 3 inches in depth, and ^ inch and ^ inch thick. The middle sleepers 

 extend throughout the length of the vessel ; those on the sides are level on 

 their upper surface, and consequently are terminated by the rising of the 

 bottom of the ship. These sleeper are tied to the bottom and are preserved 

 in their verticle position, hy inverted curves of strong angle iron, which are 

 riveted to the ribs and also up the sides. Along the upper edge of each, 

 there is an angle iron, and over the whole is riveted an iron deck J inch in 

 thickness. 



Keels. — There are two bilge keels, consisting of a middle plate, H inch 

 thick, and two angle irons, 5 inch each way hy 1 inch thick. Tiiese bilge 

 keels are 110 feet long, and their under edges are on the same horizontal 

 level with the under side of the keel, so that in docking the ship, if long 

 baulks of timber were extended across the dock hy way of blocks, the weight 

 of the body of the ship (where the boilers and machinery are placed), is 

 supported at given parallel distances on both sides of the keel, all risk of 

 str.iining it, or the machinery, is avoided, and the vessel is not obliged, in 

 the usual manner, to rest uuoa her keel, until the bilge shores can be got 

 under. 



