122 THE HISTORY OF SCIENCE 



Correspondence had already been established with 

 the Royal Society of London. It is not diffi- 

 cult to see in Franklin the same spirit that had ani- 

 mated Hartlib, Boyle, Petty, 1 Wilkins, and their 

 friends one hundred years before. In fact, Franklin 

 was the embodiment of that union of scientific ideas 

 and practical skill in the industries that with them 

 was merely a pious wish. 



In this same year of 1743 an eclipse of the moon, 

 which could not be seen at Philadelphia on account 

 of a northeast storm, was yet visible at Boston, 

 where the storm came, as Franklin learned from his 

 brother, about an hour after the time of observation. 

 Franklin, who knew something of fireplaces, ex- 

 plained the matter thus : " When I have a fire in 

 my chimney, there is a current of air constantly 

 flowing from the door to the chimney, but the be- 

 ginning of the motion was at the chimney." So in 

 a mill-race, water stopped by a gate is like air in a 

 calm. When the gate is raised, the water moves for- 

 ward, but the motion, so to speak, runs backward. 

 Thus the principle was established in meteorology 

 that northeast storms arise to the southwest. 



No doubt Franklin was not oblivious of the prac- 

 tical value of this discovery, for, as Sir Humphry 

 Davy remarked, he in no instance exhibited that 

 false dignity, by which philosophy is kept aloof from 

 common applications. In fact, Franklin was rather 

 apologetic in reference to the magic squares and 



1 See The Advice of W. P. to Mr. Samuel Hartlib for the Ad- 

 vancement of some Particular Parts of Learning, in which is advo- 

 cated a Gymnasium Mechanicum or a College of Tradesmen with 

 fellowships for experts. Petty wanted trade encyclopedias pre- 

 pared, and hoped for inventions in abundance. 



