412 Messrs. J. J. Thomson and H. F. Newall. [June 16, 



Description of Apparatus. 



The condenser consisted of two copper cylinders, the outer one 

 being formed into a pot 12 inches deep and 4 inches in diameter, 

 closed at the bottom by a rounded end carefully worked inside, the 

 inner one, 8 inches long and 3 inches in diameter, being closed, 

 rounded off: at both top and bottom, and carefully worked outside. The 

 outer cylinder was held in position on a bracket attached to a brick 

 wall, and was always connected to earth through the gas-pipes ; the 

 inner one was suspended by a silk thread, 5 feet long, also from a 

 bracket on the wall, vertically above the first, and was connected to 

 an insulated mercury cup by means of a thick wire, which was care- 

 fully soldered into the top of the cylinder, and bent into a loop to 

 attach the silk thread to. The figure shows the arrangement in eleva- 

 tion, the outer cylinder being represented as transparent, to show the 

 inner cylinder and attachment. 



The liquid to be experimented on was poured into the outer pot, 

 and the inner cylinder was lowered into it, both being set vertical by 

 means of a plumb-line. It was found necessary to load the inner 

 cylinder with shot to keep it sunk in the liqaid. 



The suspension by a single silk thread was found very satisfactory, 

 as it insulated well, and avoided the introduction of solid dielectrics, 

 and the suspended cylinder if disturbed came again to rest after a 

 very few oscillations. 



The condenser was charged by means of a number (varying between 

 20 — 80) of Post Office Daniell cells, and Thomson's quadrant electro- 



