AMERICAN INSTITUTE. 565 



Wind, the application of Avhicli to locomotion on water, has 

 been the subject of improvement from time immemorial at this 

 day hardly competes with steam, whose marine career dates back 

 but sixty years. And upon land, this agent must be obviously 

 unsuccessful, for its force and direction are almost the emblems 

 of uncertainty. 



Through the process of combustion, however, that most feasible 

 of all sources, caloric has been employed with signal success. 

 The question now arises, by its application to what agent will it 

 produce the greatest power, at the least cost. Air, the cheapest 

 element, has been applied with comparatively indifferent, yet 

 positively marked, success. When we consider tliat all vapors 

 and gases expand equally by increase of temperature, it would 

 appear that the true economist w^ould start with a gas, which like 

 air is ready made, rather than to waste heat enough to vaporize 

 a fluid. The conversion of water into steam requires more than 

 1000° of heat, after wiiich expenditure, its jn-essure is only equal 

 to that of the atmosphere. But the moment such an idea is re- 

 duced to practice the fallacy appears. To be rendered productive 

 of power the gas or vapor must be forced into a heater, made the 

 maximum pressure, and then expanded. Then since the volume 

 of air at 15 pounds per square inch, w^hen it enters the pump of the 

 air engine, is 1,700 times greater than the volume of steam at the 

 same pressure, in the shape in which that steam enters the pump 

 of its engine, viz : water, increased friction and bulk, at once 

 reverse the comparative values of these agents. If air is used 

 at a high pressure, the vessel in which it is supplied with its 

 power-giving heat, though composed of the most costly materials 

 will hardly last through a trial trip. If it is employed at a low 

 pressure, say 15 pounds, the enormous capacity of the vessel in 

 which its power is converted into motion, would at least in land 

 locomotion, entirely destroy its utility. But on the other hand, 

 in the generation of steam, the presence of the w^ater in the one 

 case prevents the destruction of the heater, and in the other it 

 diminishes by lialf, the size of the cylinder, through the agency 

 of another property of steam, viz : instantaneous condensation, 

 by the absence of heat. While the temperature of the air heater 

 must be 5'JO degrees, the sensible heat of the water, and of its 

 heater, in the production of the same force, is only 25') degrees. 

 A still greater difference arises as the pressures increase. At 90 

 lbs., the sensible heat of water is 324 degrees, while that of air 

 would be more than 3,000 degrees or near tliat of melting iron. 



