180 THE POPULAR SCIENCE MONTHLY. 



these facts is equally certain. It is, therefore, sure that all of 

 space that is accessible to us is not void, but is filled with a sub- 

 stance capable of entering into vibration the ether. But while 

 we have clear notions of the geometrical conditions of the phenom- 

 ena that occur in this matter, their physical nature is very ob- 

 scure ; and what we know of the properties of the substance is 

 full of contradictions. Comparing the waves of light with those 

 of sound, they were regarded as elastic. But only longitudinal 

 waves have been observed in fluids, and under the conditions of 

 matter transverse waves are impossible in them. We have been 

 obliged, therefore, to assume that the ether acts as a solid body. 

 But when we regard the motions of the stars and endeavor to de- 

 termine their conditions, we have to affirm that ether behaves like 

 a perfect fluid. Without endeavoring at present to explain the 

 contradiction that presents itself here, we pass to electricity ; it 

 may throw some light on the problem. 



Most of the persons who ask what electricity is have no doubts 

 respecting its real existence, and only expect a description of the 

 properties of the singular substance. With scientific man, the 

 problem takes the form, Does electricity really exist ? Do not 

 electric phenomena, like the other ones, go back to properties of 

 ether and ponderable matter ? Our knowledge does not as yet 

 permit us to answer this question affirmatively. Material elec- 

 tricity still has a place in our conceptions, and the old and fa- 

 miliar idea of two kinds attracting and repelling one another, 

 to which are attributed actions at a distance resembling intel- 

 lectual qualities, still persists in current language. This theory 

 dated from the time when Newton's law of gravitation having 

 been confirmed by astronomy, the idea of action at a distance 

 without the intervention of a medium was familiar. Electric and 

 magnetic attractions were thought to obey the same law as gravi- 

 tation ; and, admitting a similar action at a distance, the phenom- 

 enon was supposed to be explained in the simplest manner, and 

 the limits of knowledge on the subject to have been reached. A 

 different aspect was presented when in this century the reciprocal 

 action of currents and magnets was discovered, an action infinite- 

 ly variable, in which motion and time played a great part. In 

 the necessity of increasing the number of actions at a distance to 

 complete the theory, the simplicity which gave it its scientific 

 probability disappeared. Simple formulas and general and ele- 

 mentary laws were then sought, of which Weber's law was the 

 most important tentative. Whatever may be thought of the ex- 

 actness of these essays, they formed an exceptional system and a 

 seductive whole, a magic circle, which one could not leave after 

 having once entered it. The road was one that could not lead to 

 the truth. It required a fresh mind to resist the current, one 



