856 Transactions of the American Institute. 



Still further, we will inquire, what are the conditions, physical and 

 intellectual, which best aid our progress in perfecting the steam-engine. 



This most important problem may be stated in its most general, yet 

 definite, form as follows : 



To- construct a machine which shall, in the most perfect manner 

 possible, convert the kinetic energy of heat into mechanical power, 

 the heat being derived from the combustion of fuel, and steam being 

 the receiver and the conveyer of that heat. 



The problem embodies two distinct and equally important inquiries. 



The first : What are the scientific principles involved in the problem 

 as stated ? 



The second : How shall a machine be constructed that shall most 

 efficiently embody, and accord with, not only those scientific principles, 

 but also all of those principles of engineering practice that so vitally 

 affect the economical value of every machine ? 



The one question is addressed to the man of science, the other to 

 the engineer. They can be satisfactorily answered, even so far as our 

 knowledge at present permits, after studying with care the scientific 

 principles involved in the theory of the steam-engine under the bfst 

 light that science can afford us, and by a careful study of the various 

 steps of improvement that have taken place, and of accompanying 

 variations of structure, analyzing the effect of each change, and 

 tracing the reasons therefor. 



The theory of the steam-engine is too important and too extensive 

 a subject to be treated here in even the most concise possible manner. 



I can only attempt a plain statement of the course which seems to 

 be pointed out by science as the proper one to pursue in the endeavor 

 to increase the economical efficiency of steam-engines. 



The teaching of science indicates that success in economically deriv- 

 ing mechanical power from the energy of heat motion, will, in all cases, 

 be the greater as we work between more widely separated limits of 

 temperature, and as we more perfectly provide against losses by dissi- 

 pation 01 heat in directions in which it is unavailable for the produc- 

 tion of power. 



Scientific research has proved that, in all known varieties of heat 

 engine, a large loss of effect is unavoidable from the fact that we 

 cannot reduce the lower limit of temperature, m working, below a 

 point which is far above the absolute zero of temperature ; far above 

 that point at which bodies have no heat motion ; the point correspond- 

 ing to the mean temperature of the surface of the earth is the lower 

 limit. 



