THE CONQUEST OF NATURE 



enough, the very newest explanations are not so very 

 far away from some eighteenth-century theories which 

 for a long time were looked at askance if not altogether 

 discarded. In particular, the theory of Benjamin 

 Franklin, which considered electricity as an immaterial 

 fluid bearing certain curious relations to tangible matter, 

 is found to serve singularly well as an aid to the inter- 

 pretation of the very newest experiments. 



FRANKLIN'S ONE-FLUID THEORY 



Such being the case, we must consider this theory of 

 Franklin's somewhat in detail. Perhaps we cannot do 

 better than state the theory in the words of the celebrated 

 physicist, Dr. Thomas Young, as given in his work on 

 natural philosophy, published in 1807. By quoting 

 from this old work we shall make sure that we are not 

 reading any modern interpretations into the theory. 

 "It is supposed," says Young, "that a peculiar ethereal 

 fluid pervades the pores, if not the actual substance of 

 the earth and of all other material bodies, passing 

 through them with more or less facility, according to their 

 different powers of conducting it; that particles of this 

 fluid repel each other, and are attracted by particles of 

 common matter; that particles of common matter also 

 repel each other; and that these attractions and repul- 

 sions are equal among themselves, and vary inversely 

 as to squares of the distances of the particles. The 

 effects of this fluid are distinguished from those of all 

 other substances by an attractive or repulsive quality, 

 which it appears to communicate to different bodies, 



