THE CONSERVATION OF ENERGY 



be raised above the ground in order that its falling 

 force may be equivalent to the raising of the tem- 

 perature of an equal weight of water from o to i 

 centigrade. The attempt to show that such an 

 equation is the expression of a physical truth may 

 be regarded as the substance of the foregoing re- 

 marks. 



" By applying the principles that have been set forth 

 to the relations subsisting between the temperature 

 and the volume o gases, we find that the sinking of a 

 mercury column by which a gas is compressed is equiv- 

 alent to the quantity of heat set free by the compres- 

 sion ; and hence it follows, the ratio between the capac- 

 ity for heat of air under constant pressure and its ca- 

 pacity under constant volume being taken as = 1.421, 

 that the warming of a given weight of water from 

 o to i centigrade corresponds to the fall of an equal 

 weight from the height of about three hundred and 

 sixty-five metres. If we compare with this result the 

 working of our best steam-engines, we see how small a 

 part only of the heat applied under the boiler is really 

 transformed into motion or the raising of weights ; and 

 this may serve as justification for the attempts at the 

 profitable production of motion by some other method 

 than the expenditure of the chemical dilYcrcnce be- 

 tween carbon and oxygen more particularly by the 

 transformation into motion of electricity obtained by 

 chemical means. ' 



MAYER AND HELMHOLTZ 



Here, then, was this obscure German physician, lead- 

 ing the humdrum life of a village practitioner, yet see- 



267 



