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IX. — On the economical production of Mechanical Effect 

 from Chemical Forces. 



By J. P. Joule, F.R.S., &c. 



[Riad April QUi, 1852.] 



Perhaps the most important applications of dynamical 

 theory are those which refer to the production of motive 

 power from chemical and other actions. To point out the 

 rules for constructing an engine which shall approach per- 

 fection as nearly as possible, and to determine the quantity 

 of work which ought to be evolved by a perfect engine of 

 any given class, are objects of the greatest consequence in 

 the present state of society, and which have in fact been to a 

 great extent already accomplished by the labours of those who 

 have taken a correct view of the nature of heat. I intend on 

 the present occasion to submit to the Society some of the 

 laws which have been recently arrived at by Professor Thomson 

 and myself, and to offer some hints as to the means of carrying 

 out into practice the deductions of theory. 



Engines which derive their power from the operation of 

 chemical forces may be divided into three classes. The first 

 class comprises those exquisite machines in which chemical 

 forces operate by the mysterious intervention of life, whether 

 in the animal or vegetable creation. The second class includes 

 machines in which the chemical forces act through the inter- 

 vention of electrical currents, as in the ordinary revolving 

 electro-magnetic apparatus. The third comprises those 

 engines in which the chemical forces act through the inter- 

 vention of the heat they produce ; these, which may be 



