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 conditions 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 conditions 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
