38 ANNUAL OF SCIENTIFIC DISCOVERY. 



of an inch thick, the other of iron plates 0'414 of an inch in thickness. The 

 steel boiler was tested by hydraulic pressure up to 195 pounds per square 

 inch. Both boilers were worked for about a year and a half under 65 

 pound p : essure. At the end of that time there was less scale in the 

 steel than in the iron boiler. The steel boiler generated 25 per cent more 

 steam and evaporated an average of 11*66 cubic feet of water per hour; 

 the iron evaporated 9*37 cubic feet. The quantity of coal consumed per 

 12 hours was 2,700 for the steel, and 2,972 for the iron boiler. The 

 plates of the steel boiler directly over the fire were found to be uninjured 

 while those of the other were worn out. The advantages of the steel 

 boiler are strength, lightness, rapidity of evaporation, durability under 

 heat, the securing of more perfect riveting, and comparative freedom fr< m 

 scale. 



NEW MECHANICAL ACTION OF STEAM. 



In a recent English invention it is claimed "that the expansive 

 force of the steam is made to act equally on two pistons, and force 

 them apart with the power due to the area of the pistons and the pres- 

 sure of the steam, and that the force thus exerted on two pistons is 

 united and conveyed to the crank shaft ; whereas, in steam engines of 

 the usual construction, with a piston working in a cylinder, half the 

 force exerted is always acting on one of the ends of the cylinder " 



NEW CALORIC ENGINE. 



A new caloric engine, invented by Mr. Roper of Boston, Mass, has 

 the following peculiarities. It is designed to be used where small 

 power is required ; and the main novelty about it is, that it does not use, 

 upon the piston, common a r heated, but only the products of comhus- 

 tion. The air to sup] ly oxygen for the combustion of anthracite coal is 

 punr;ccl i:i; the caibon is i; ; rued rapidly and completely, under pressure, 

 and the resulting carbonic acid gas and uncombined nitrogen gas from 

 the i:ir, are pa^ed from the g> nerator to the piston, which is in the form 

 of a hollow plunger, -so arranged that it is packed and tilted only at the 

 top, where there is the least heat. Is this way the common difficulty of 

 lubricating a hot cylinder and piston is obviated. The generator of heat 

 is surrounded with firebrick or soapstone, which prevents the iron from 

 being burnt. The engine is single acting, that is, the power is ap- 

 plied to the piston moving in one direction, during which movement the 

 air to feed the fire is pumped in; the momentum acquired at the same 

 time, by a balance or fly-wheel, is used to carry the piston back to its 

 original position. 



OX OUR FUTURE LOCO-MOTION. 



"It would be presumptuous to augur that steam locomotives and 

 their trains will erelong iail to meet the demands of society ; but it 

 would be much more so to conclude that they comprise the perfection 

 of mechanical resource, and are to be the ne plus ultra of land travel- 

 ing for all time to come. In nature nothing is born or matured at 

 once ; and in art nothing springs complete iroin human brains. In- 

 ventions, like plants, are designed to grow until they are ripe ; and 

 wl*m all is got out of them that" can be, to give place to others. When 

 one has fulfilled its promise in the front ranks of civilization, it is to 



