WASTED FORCES. 291 



be possible to attain. Suppose we take steam, the almost universal 

 motive power of to-day, as an example, and put the inquiries, What 

 ought we to get out of it and what do we get out of it ? And when I 

 am through, I think that many of my hearers, who have heretofore en- 

 tertained the belief that steam-engineering was a field that had been so 

 thoroughly worked up that but little remained to be accomplished in 

 the direction of increasing the duty of our steam-motors, will be will- 

 ing to acknowledge themselves mistaken. 



To get at the practical duty of a steam-engine, we must begin with 

 the source of the power, the steam-generator popularly and most 

 inappropriately called the steam-boiler ; and, as the source and origin 

 of the power generated in the boiler and directly traceable to the com- 

 bustion of the fuel, it is evident that we must begin with that. Let us 

 inquire, therefore, what power we ought to get from a perfect steam- 

 engine burning pure coal, and then compare it with what we do get in 

 the best steam-engine practice of to-day. 



To understand the deductions I shall shortly make in getting at 

 this comparison between theory and practice, I prefer to invite you 

 to follow me through a few theoretical considerations, rather than ask 

 you to accept the conclusions simply on my bare assertion. 



It has long been known that a definite relation exists between the 

 quantity of heat developed in a given operation and the quantity of 

 mechanical force (manifested as work) that could be obtained from 

 that heat. The absolute nature of this equivalency is tacitly recog- 

 nized, though perhaps imperfectly comprehended in the practice of 

 every branch of industry employing heat as a source of power ; for 

 it is this fact which establishes the dimensions of the steam-boiler, and 

 the several proportions of the engine to do the work required of it. 

 The steam-engine, in simple language, is simply an apparatus for turn- 

 ing heat into work ; and it is, therefore, quite possible to express the 

 value of a given quantity of the form of energy we call heat in terms 

 of mechanical energy that we call " work " ; and scientific investi- 

 gation has established an admirable unit for this comparison in the 

 " foot-pound" that is, the force required to raise a pound weight to 

 the height of one foot. 



Now, to estimate the value of heat in terms of work, it was found 

 necessary to determine the amount of mechanical force necessary to 

 raise the sensible heat of one pound of water one degree in tempera- 

 ture. This amount has been carefully determined by several eminent 

 savants, and has been given the name of the "mechanical equivalent 

 of heat." The value of this constant has been found to be 772 foot- 

 pounds that is to say, the mechanical energy possessed by a body 

 weighing one pound, after falling from a height of 772 feet, would, if 

 it could all be converted into the form of energy we call heat, be 

 exactly sufficient to raise the temperature of one pound of water 1 

 Fahr. (where the centigrade thermometer is employed, this constant 



