185 
[DolbeAr. 
To explain a phenomenon therefore is to point out the antece- 
dent motions and the conditions under which a transformation 
has been effected. To say that a given phenomenon is the result 
of attraction or repulsion or chemism is not to explain it at all. 
If, however, one does not understand the modus operandi by 
which the change has been effected, but does understand the 
physical necessity of recognizing physical antecedents of an ex- 
changeable sort he will not mistake such terms for ultimate causes 
of change. 
The work of Davy, Faraday and Joule already alluded to set- 
tled the question as to the nature of all the forms of energy, 
although there are some now who are unable to see the logic of 
the question. Thus, if heat and electricity be quantitatively re- 
lated, and heat be vibratory molecular motion, and a given body 
becomes electrified at the expense of the temperature of the body, 
there must have been a change in the character of the motions 
present and electricity must be as much a mode of motion as heat 
is. In like manner if electricity and chemism be quantitatively 
related as Faraday’s laws state and if there be likewise constant 
thermal relations between chemical reactions, as is implied in all 
thermo-chemical problems, then is chemism traceable to antece- 
dent motions of an atomic and molecular sort, and it will be ex- 
plained in a complete physical sense when these purely mechanical 
relations are fully pointed out. The first step must then be to 
inquire what known forms of energy, if any, plainly condition chem- 
ism. Here at the outset we have the laws of thermo-chemistry, 
founded in thermo-dynamics. In all chemical reactions whether of 
composition or decomposition there is an exchange of energy meas- 
ureable in foot-pounds, or calories. Now if we take the simple 
example of the thermal effect due to the combination of hydrogen 
and oxygen, we know that if a gram of hydrogen combines with 
oxygen to form water, there will be developed 34,000 calories, the 
calorie representing the amount of heat required to raise a gram 
of water one degree centigrade, and which in turn represents in 
amount of work 426 gram-metres. 34,000 X 423 = 14,484,000 
gram-metres, work. We also know, that to separate the hydro- 
gen from the oxygen will require the expenditure of the same 
amount of work. It therefore is a measure of the chemism of 
that amount of hydrogen and oxygen. 
In like manner it is deduced from the second law of theorm- 
