THE MOTIVE POWER OF HEAT. 117 



THE MOTIVE POWER OF HEAT. 



By C. K. EDMUNDS, 



JOHNS HOPKINS UNIVERSITY. 



A/TR. ALFRED RUSSEL WALLACE, in his 'Wonderful Cen- 

 -L>-*- tury,' describes those great material and intellectual achieve- 

 ments which especially distinguish the nineteenth century from any and 

 all of its predecessors, and shows how fundamental is the change they 

 have effected in our life and civilization. From a comparative esti- 

 mate of the number and importance of these achievements, he concludes 

 that not only was the century just passed superior to any one that had 

 gone before, but that it must in its results be compared with the whole 

 preceding historical period. It, therefore, marks the beginning of a 

 new era of human progress. 



There appears, however, upon looking back through the long, dark 

 vista of human history, one step in material progress that seems to be 

 really comparable with several steps of modern times. It was when 

 fire was first utilized and became the servant and friend rather than 

 the master and enemy of man. From that day to this, fire, in 

 various forms and in ever-widening spheres of action, has been the 

 greatest, the essential factor in that increase of man's power over 

 nature, which has in turn been a chief means of developing what we 

 term civilization. As Mr. Fernald, in his 'Gulf of Fire,'* points out, 

 all men, however widely separated by millenniums of time and by 

 utmost range of space, by mountains, deserts and oceans, by color, 

 language and occupation, by custom and religion, all agree in this 

 they make fire a servant and a friend. Mr. Fernald shows how the 

 firebrand draws an impassable line between man and the brute creation, 

 and graphically depicts the part played by the ancient element fire in 

 aiding man along that upward path which, having entered, he had only 

 to follow on to make the universe his own. 



Steam engines in their infancy were known as 'fire' (i. e., heat) 

 engines; and, in point of fact, the older term is the more correct, 

 because the water or steam is used only as a convenient medium 

 through which the form of energy which we call heat is made to 

 perform the required mechanical operations. The claims of the steam 

 engine (as locomotive, marine and stationary) to the greatest share 

 in the marvelous material progress of the nineteenth century are too 



* Harper's Monthly Magazine, July, 1902. 



