RECENT PROGRESS IN PHYSICS. 381 



The copper wire, finely pointed and gilded at its upper 

 end, is about one Paris line in diameter, and is surrounded 

 with very fine platinum points, which are most easily 

 made in the following way : The wire is covered with tin 

 solder as far as the platinum points extend ; then, as 

 shown in fig. 18, it is wound with the finest platinum 

 wire, which is fused in a spirit lamp where it touches the 

 ^ )pper point; the loops are then cut, and arranged as 

 exhibited in fig. 17. 



The conducting wire d e, fig. 19, [which is a repetition of fig. 17,] of 

 copper, is soldered to the ring at e. At d it has a small tin plate which 

 turns off the rain. A similar plate is placed on the rod at o for the 

 same purpose. On the lower end of the conducting wire e d at c, a 

 small copper socket is soldered and arranged so as to receive the con- 

 ducting wire coming from the chamber. The window frame is bored 

 in the corner, for the purpose of fastening the conductor in a glass 

 tube well coated with shellac, and bringing it into the chamber per- 

 fectly insulated. At b the wire is bent downwards, and connected 

 with the electrometer E placed at the side of the window, and beyond 

 the immediate influence of the sun's rays. 



liomershansen uses two electrometers, standing in the same case, 

 namely : a pile electrometer, and one constructed on the plan of Bell- 

 man, which has been already described. 



