THE KINETIC THEORY OF MATTER 421 



the middle of the nineteenth century, when it gave birth to the prin- 

 ciple of conservation of energy, a generalization which grew immedi- 

 ately and inevitably out of the mechanical theory of heat as it lay in 

 the minds of Eumford, Joule and their co-workers. Between 1860 

 and 1890 the proofs of the kinetic hypothesis came in so rapidly 

 through the brilliant work of such masters as Joule, Clausius, Maxwell, 

 Kelvin and Boltzmann that the scientific world began to be con- 

 vinced, and only here and there was found a man of standing among 

 the scoffers. Then, about 1887, a reaction set in, and the school of 

 energetics arose in Germany, which attempted to force the principle 

 of conservation of energy to devour its ovm mother. The most spec- 

 tacular of the onslaughts was made by Ostwald, who in 1895 wrote a 

 widely circulated essay, entitled " The Demolition of Scientific Ma- 

 terialism," elsewhere printed under the title, " The Route of Modern 

 Atomism." Led by such a bell-wether, the sheep began to jump back 

 over the wall, and the results of that backward movement are still felt 

 in the United States, particularly in high-school texts, despite the fact 

 that to-day the opposition among scientific men to the kinetic hypoth- 

 esis is absolutely gone, and even Ostwald has admitted his error. In- 

 deed, so direct and so convincing is now the evidence that it is not too 

 much to say that any one who wishes can now have immediate ocular 

 demonstration of the perpetual dance of the molecules of matter. 



But since we are here as much concerned with the atomic or granular 

 theory of electricity as with the kinetic theory of matter, let us turn for 

 a moment to consider the present status of our knowledge as to 

 the nature of electricity. Unlike the kinetic theory of matter, the 

 granular theory of electricity can, boast of no great antiquity. Indeed, 

 in its present form it is but ten or fifteen years old, and in no form is it 

 more than one or two hundred years old. For there are no electrical 

 theories of any kind which go back of our own Benjamin Franklin. It 

 is true that the Greeks discovered that rubbed amber had the power of 

 attracting to itself light objects placed in its neighborhood, but this is 

 all until A.D. 1600, when Queen Elizabeth's surgeon, Gilbert, found 

 that a glass rod and some twenty other bodies, when rubbed with silk, 

 acted like the rubbed amber of the Greeks, and he consequently decided 

 to describe the phenomenon by saying that the glass rod had become 

 electrified (amberized, electron being the Greek word for amber) or 

 had acquired a charge of electricity. In 1733, Dufay, a French phys- 

 icist, further found that sealing wax, when rubbed with cat's fur, was 

 also electrified, but that it differed from the electrified glass rod, in 

 that it strongly attracted any electrified body which was repelled by 

 the glass, while it repelled any electrified body which was attracted by 

 the glass. About 1847, Benjamin Franklin adopted the following 

 purely arbitrary convention, and said. We will consider that there are 



