MECHANICS AND USEFUL ARTS. 49 



The simple construction of the caloric engine, and the small quan- 

 tity of coal to be handled, will reduce the number of engineers and 

 firemen, in the aggregate, to less than one-fourth the compliment 

 required for steamers. This great reduction in the number of men, 

 whose duties are incompatible with strict cleanliness, will still further 

 promote a purer state of atmosphere in caloric ships than in steamers. 

 Ao-ain, as no smoke whatever is produced, when anthracite coal is 

 employed, the masts and rigging of the caloric ship will be as clean 

 as in sailing vessels. 



The following are some of the dimensions and statistics of this ship : 

 Length, 250 feet; beam, 40; hold, 27; tonnage, 2,000 to 2,200; 

 diameter of wheels, 32 feet; face of wheel, 1H feet; power of 

 engines, 600 horse ; consumption of coal per day, (24 hours,) 8 tons ; 

 number of men in engine department, 10 ; number of sailing crew, 

 20 ; passenger accommodation for 200, with room for enlargement to 

 double the capacity; room for 1,500 tons freight; cost, in the neigh- 

 borhood of $300,000. 



The scientific and commercial world will watch with deep anxiety 

 the result of this grand experiment with the caloric engine. Should 

 it fail, a contingency, by the way, which its friends deem most improb- 

 able, the world will lose nothing, and the experimenters comparatively 

 little, since the strong and beautiful ship may be put to other uses in 

 ordinary steam navigation. Should it succeed, the days of steam are 

 numbered. 



OX CERTAIN rOIXTS IX THE COXSTRUCTIOX OF MARIXE BOILERS. 



MR. J. SCOT RUSSELL, the celebrated ship architect of England, 

 having arrived at certain theoretical results relative to the construc- 

 tion of marine boilers, put them into practice, about ten years back, 

 in designing the boilers for the Royal Mail Steam Packets Clyde, 

 Tay, Tweed, and Teviot ; and as they have been in constant work 

 ever since, running from 42,000 miles to 48,000 miles per annum, 

 without material repairs, he believes their durability, combined with 

 effective combustion, and economy of fuel, to have been fully estab- 

 lished. The principles upon which these boilers are constructed, 

 differ from those generally recognized. In the first place, it was 

 considered that a judicious distribution of the most intensely heated 

 surfaces would be conducive to durability ; and for this purpose, 

 instead of returning the ilues over the furnaces, the top of the fur- 

 naces and the hottest flues were brought to the surface of the water, 

 and the cooler, or return flues, were taken to the bottom of the water. 

 The water was admitted at the bottom, and was gradually warmed as 

 it rose, the greatest heat being imparted at the last moment, by which 

 means the "bubbles of steam were prevented from accumulating in 

 contact with intensely heated metal. In the next place, the capacity 

 of the furnaces, or fireboxes, was unusually large, and their height 

 above the incandescent fuel much greater than usual. The evapo- 

 rating surface in these boilers was also much more than customary, 



