250 POPULAR SCIENCE MONTHLY. 



and now we call it a wave motion in the ether, and say there is no such 

 thing as light, it is merely a condition of the ether in the same sense 

 as heat is a condition of matter; and there are some physicists who 

 go farther and declare it to be only an optical illusion, a physiological 

 phenomenon and does not exist apart from the mechanism of the eye. 

 Such have proposed we discard the word light from physical science, 

 seeing it is only a condition of the optical apparatus. At any rate, 

 the nature of light is now so well known and understood that no one 

 thinks of asking the question 'What is light,' hut the answer we give 

 is a long remove from the answer expected a hundred years ago. 



Here on the threshold of the new century we are confronted with 

 the question 'What is electricity?' and the answer implied by the 

 question seems to demand a something which could be described by one 

 who knew enough, as one would describe some new mineral or gas 

 or thing. Some eminent scientific men are befogged by the question, 

 say it is some ultimate unknowable thing, and hopeless as an inquiry. 

 If it be a something it must be described by its constant properties 

 as other things are. If it be unlike everything else then it can not be 

 described by terms that apply to anything else. All material things 

 have some common properties. A glowing coal is an incandescent 

 solid, a flame is an incandescent gas, but neither glow nor flame exists 

 apart from the matter that exhibits the phenomena. Both are condi- 

 tions of particular kinds of matter. 



If electric phenomena are different from gravitative or thermal 

 or luminous phenomena it does not follow that electricity is miraculous 

 or that it is a substance. We know pretty thoroughly what to expect 

 from it, for it is as quantitatively related to mechanical and thermal 

 and luminous phenomena as they are to each other ; so if they are con- 

 ditions of matter, the presumption would be strongly in favor of 

 electricity being a condition or property of matter, and the question 

 'What is electricity?' would then be answered in a way by saying so, 

 but such an answer would not be the answer apparently expected to 

 the question. To say it was a property of matter would be not much 

 more intelligible than to say the same of gravitation. At best it 

 would add another property to the list of properties we already credit 

 it with, as elasticity, attraction and so on. In any case the nature 

 of electricity remains to be discovered and stated in terms common to 

 other forms of phenomena, and it is to be hoped that long before this 

 new century shall have been completed, mankind will be able to form 

 as adequate an idea of electricity as it now has of heat. 



What thoughtful person has not asked ' What is life ? ' Many and 

 long answers have been given to this question. One has said 

 ' Electricity is life/ Another ' Life is the continuous adjustment of 

 the internal relations to the external relations.' Which definition tells 

 rather what life does than what it is. Some have imagined it to be 



