ENERGY IN GENERAL. 83 



system, adopted by the Norwegian chemists, Guldberg 

 and Waage, by means of the product of the masses 

 and of a force, or co-efficient of affinity, which depends 

 on the nature of the substances which are brought to- 

 gether, on the temperature, and on the other physical 

 circumstances of the reaction. On the other hand, 

 the researches of M. Berthelot enable us in many 

 cases to obtain an indirect valuation in terms of the 

 equivalent heat. 



Its Tzvo Forms. — It is interesting to note that 

 chemical energy may also be regarded from the two 

 states of potential and kinetic energy. The coal- 

 oxygen system, to burn in the furnace of the steam 

 engine, must be primed by preliminary work (local 

 ignition), just as the weight that is raised and left 

 motionless at a certain height requires a small 

 effort to be detached from its support. When this 

 condition is fulfilled, energy is at once manifest. 

 We must admit that it existed in the latent state, in 

 the state of chemical potential energy. Under the 

 impulse received, the carbon combines with the 

 oxygen and forms carbonic acid, C + 2O becomes 

 CO2; potential energy is changed into actual chemical 

 energy, and immediately afterwards into thermal 

 energy. W^e should have only a very incomplete and 

 fragmentary view of the reality of things if we were 

 to consider this phenomenon of combustion in isolation. 

 We must consider it in connection with what has 

 actually created the energy which it is about to 

 dissipate. This antecedent fact is the action of the 

 sun upon the green leaf. The carbon which burns in 

 the furnace of the machine comes from the mine in 

 which it was stored in the form of coal — that is to say, 

 of a product which was vegetable in its primitive form, 



