60 



HABIT AND INTELLIGENCE. 



[chap. 



Proposed 

 addition 

 to it. 



Heat-units 



Thermal 

 equiva- 

 lents. 



Thermo- 

 negative 

 and 



thermo- 

 positive 

 com- 

 pounds. 



from the potential into the actual state, and given out as 

 heat or electricity. Yet energy has as real an existence, 

 and is as definitely measurable hy quantity, as oxygen or 

 hydrogen ; and consequently, in order to give a full 

 account of what takes place so far as a formula can give 

 it, the equation ought to state not only what elements 

 combine, and in what proportions, but also how much 

 energy is given out in the act of their combining. 



I propose to do this as follows. The quantity of heat 

 that will raise the temperature of a pound (or any other 

 imit- weight) of water by 1° centigrade is called by writers 

 on the subject a heat-tmit. As already stated, the com- 

 bination of a pound of hydrogen with oxygen, so as to 

 form water, gives out enough of heat to raise the tem- 

 perature of 34,462 pounds of water by 1° centigrade. In 

 other words, 34,462 heat-units are given out in the forma- 

 tion of water, and 34,462 is the thermal equimlcnt of 

 water. I propose to write 6 as the symbol of a heat-unit. 

 The symbolical expression for water will then be : — 



HOi — 34,462 6; 



indicating by the use of the negative sign that the heat, 

 or its equivalent in electricity, has heen iMrtcd tvith : and 

 when the sign of the thermal equivalent is negative, I 

 propose to caU'the compound thcrmo-ncgative. All com- 

 pounds formed by the spontaneous combustion of their 

 elements are thermo-negative : that is to say, heat has 

 been given out in their formation. Products of perfect 

 combustion, such as water and carbonic acid, are neces- 

 sarily thermo-negative. 



But with some substances the sign of the thermal 

 equivalent is positive : and I propose to call them thermo- 

 positive substances. Nitrous oxide is one of these. Its 

 symbol, written as I propose, is^ 



NO + 9,232^; 



1 " In the experiments of Dulong it appeared that when oxide of carhon, 

 or hydrogen, was burned in protoxide of nitrogen [nitrous oxide], a larger 

 amount of heat was evolved than when the same weights of these gases 

 were burned in oxygen. Following up this observation, Fabre and Sil- 

 bermann were led to the remarkable conclusion that protoxide of nitrogen, 



