AN UNDISCOVERED GAS. 257 



Electrical energy is the product of electric capacity into potential. 



Cliemical energy is tlie product of "atomic weight" into affinity. 



In each statement of factors the "capacity factor" is placed first 

 and the "intensity factor" second. 



In considering the "capacity factors" it is noticeable that they may 

 be divided into two classes. The two first kinds of energy, kinetic and 

 linear, are independent of the nature of the material which is subject 

 to the energy. A mass of lead offers as much resistance to a given 

 force, or, in other words, possesses as great inertia as an equal mass of 

 hydrogen. A mass of iridium, the densest solid, counterbalances an 

 equal mass of lithium, the lightest known solid. On the other hand, 

 surface energy deals with molecules, and not with masses. So does 

 volume energy. The volume energy of 2 grams of hydrogen, con- 

 tained in a vessel of 1 liter cai)acity, is equal to that of 32 grams of 

 oxygen at the same temperature and contained in a vessel of equal 

 size. Equal masses of tin and lead have not equal capacity for heat; 

 but 119 grams of tin has the same capacity as 207 grams of lead; that 

 is, equal atomic masses have the same heat capacity. The quantity of 

 electricity conveyed through an electrolyte under equal difference of 

 potential is proportional, not to the mass of the dissolved body, but to 

 its equivalent; that is, to some simple fraction of iim atomic weight. 

 And the capacity factor of chemical energy is the atomic weight of 

 the substance subjected to the energy. We see, therefore, that while 

 mass or inertia are important adjuncts of kinetic and linear energies, 

 all other kinds of energy are connected with atomic weights, either 

 directly or indirectly. 



Such considerations draw attention to the fact that quantity of mat- 

 ter (assuming that there exists such a carrier of properties as we term 

 "matter") need not necessarily be measured by its inertia or by gravi 

 tational attraction. In fact, the word "mass" has two totally distim-t 

 significations. Because we adopt the convention to measure quantity 

 of matter by its mass the word "mass" has come to denote "quantity 

 of matter;" but it is open to anyone to measure a quantity of matter 

 by any other of its energy factors. I may, if I choose, state that those 

 quantities of matter which possess equal capacities for heat are equal, 

 or that "equal numbers of atoms" represent equal quantities of matter. 

 Indeed, we regard the value of material as due rather to what it can 

 do than to its mass; and we buy food, in the main, on an atomic, or, 

 perhaps, a molecular basis, according to its content of albumen; and 

 most articles depend for their value on the amount of food required by 

 the producer or the manufacturer. 



The various forms of energy may therefore be classified as those 

 which can be referred to an "atomic" factor and those which possess 

 a "mass" fiictor. The former are in the ma>jority, and the periodic 

 law is the bridge between them — as yet an imperfect connection, for 

 the atomic factors, arranged in the order of their masses, display only 

 SM 97 17 



