48 ANNUAL OF SCIENTIFIC DISCOVERY. 



ever created in this country. The engines being placed in the centre 

 of the vessel, admit of a better form of midship section than in 

 steamships. Of this the builders have availed themselves, by giving 

 such a rise to the floor, that strength and easy lines for passing 

 through the water, are appropriately combined. The floor of the 

 vessel is built entirely solid from stem to stern, and in order to give 

 additional strength to the ample timbers, the entire frame is banded 

 by a double series of diagonal braces, of flat bars of iron, let into the 

 timbers at intervals of about three feet, each series being riveted 

 together at all the points of intersection. In addition to the ordinary 

 central keelsons, there are six engine keelsons, bolted on the top of 

 the floor timbers, for three-fourths of the length of the ship. On 

 these keelsons the bed-plates of the engines are secured by bolts 

 passing through the floor timbers. These bed-plates extend over the 

 entire area occupied by the engines, and present a continuation of 

 iron flooring, not witnessed in any steamship. The security thus 

 attained is further enhanced by dispensing entirely with the numer- 

 ous holes through the bottom of the vessel, which in steamers are 

 necessary, and have often brought that class of vessels to a sinking 

 condition. The engines being arranged in the centre of the vessel, 

 the decks are not cut off as in steamers ; and as the whole of the 

 machinery is confined within a vertical trunk 76 feet long and 18 feet 

 wide, ample space is left on each side of the ship for state-rooms along 

 its entire length, with unbroken passages, fore and aft, on either side. 

 The freight deck also presents an unbroken area fore and aft, dimin- 

 ished only in width in the central part of the vessel. The coal being 

 carried in the bottom, at each side of the engines, the fore and aft 

 hold are clear for freight. The central arrangement of the engines 

 involves, of necessity, a central crank, and thus the spar-deck pre- 

 sents an uninterrupted area, on both sides, the ordinary objectionable 

 crank hatches being dispensed with. The slow combustion peculiar 

 to the caloric engines renders the huge smoke funnel unnecessary. 

 A short pipe to carry off' the gases produced by the combustion in the 

 furnaces takes its place in the caloric ship. The absence of steam in 

 every form is sufficiently important in producing a more pleasant 

 atmosphere than in steamers, but far more remarkable is the fact that 

 the quantity of air which will be drawn out of the ship by the action 

 of the supply cylinders of the engines, will exceed sixty tons in wciy/tt 

 every hour ! Each supply piston presents an area of 102 superficial 

 feet, with a stroke of six feet. <>12 cubic feet of atmospheric air 

 will therefore be drawn into the engine at each stroke ; and when 

 the engine makes fourteen strokes per minute, 8,5G8 cubic feet. But 

 as there are four supply cylinders, they will in this space of time 

 draw in 34,272 cubic feet. The weight of atmospheric air is nearly 

 l.'H- cubic feet to the pound: and thus it will be seen that 68 tons of 

 air are drawn from the interior of the ship, through the engines, and 

 passed off into the atmosphere, every hour. The effect of such an 

 extraordinary system of ventilation, in purifying the atmosphere of 

 the ship, is self-evident. 



