ELECTRIC IJNES OF FORCE. 467 



are placed in it perhaps just as the wind moves the 

 weather-cock, or causes a flag to stand out in its current. 

 He places a semicircle of wire having a number of woolen 

 threads hanging from it, transversely over his glass cylin- 

 der. The threads at first are perpendicular. Then as the 

 cylinder is rotated, no pressure of the hand being exerted 

 upon it, the threads are blown aside all in one direction 

 by the wind or eddy caused by the revolving glass; but, 

 as soon as he places his hand on the cylinder to rub it, the 

 threads immediately straighten, and every one of them 

 assumes a radial position pointing to the axis of the cylin- 

 der, while the light and the cracklings are simultaneously 

 seen and heard. He changes the position of the threads, 

 sometimes fastening the semicircle of wire below the 

 cylinder, and then the threads are compelled to stand up 

 and point to the axis; and sometimes he places the cylin- 

 der vertically with the semicircle horizontal, and then the 

 threads stand out horizontally, thus proving that the force 

 in the space about the cylinder is strong enough to direct 

 the threads in straight lines despite the tendency of the air 

 to swing them aside. The extension of the threads cer- 

 tainly depends "upon the action of some matter whose 

 direction is in straight lines toward the glass.' ' There 

 was a recognition, clearly and plainly, of the lines of elec- 

 tric force for he says that when a body is interposed be- 

 tween the threads and the glass " they lose their regular \ 

 extension and hang as their own weight causes them." 



Now follows a discovery of capital importance, but 

 which to Hauksbee is a complete puzzle. He disposes 

 two glass globes within an inch of each other, but mounted 

 in separate lathes so that they can be rotated independ- 

 ently. He exhausts the air in one and applies his hand 

 to the unexhausted globe. Then he sees the light appear, 

 not only on the globe that is rubbed, but on the exhausted 

 globe which is not rubbed. But he soon finds that motion 

 of both globes is not necessary, and that he has only to 

 bring near to the excited globe a vacuum tube to see the 



