PAPERS ON CHEMISTRY AND PHYSICS 123 



of the beaker forming the top of the chamber as shown 

 in Fig. 1. The two electrostatic field plates MM and NN 

 were made of coarse-mesh copper gauze and were held 

 in place and kept flat by being wired to large rings made 

 of small Pyrex glass rod. The upper ring with its plate 

 MM was held in place against the top of the chamber 

 simply by the tension of the two lead-in wires as shown. 

 The lower ring with its plate XX was held in place by 

 having three small legs of solid pyrex glass fused to the 

 ring and the lower ends of these in turn fused to the 

 walls of the chamber. Two only of these legs are indi- 

 cated in the figure. "Wires for electrical connection to 

 the plates were carried into the chamber through capil- 

 lary openings in the walls of the chamber as shown. In 

 the experimental forms of the apparatus, these wires 

 were held in place by filling the capillary tubes with 

 "Bank of England" sealing wax. The plug P, on the 

 ■ tip of which the radioactive material was carried, was 

 ground into a glass seat placed midway between the two 

 plates. Finally, the mouth of the beaker was drawn 

 down and sealed to a tube of smaller diameter, which 

 was in turn drawn down to accommodate the stout 

 walled rubber bulb used in actuating the apparatus. A 

 small side branch tube, T, was provided for the intro- 

 duction of water into the apparatus. The necessary 

 electrical connections are shown in Fig. 1. 



The procedure in operating the apparatus is, briefly, 

 as follows : Fill the bulb and tube with water up to the 

 level A. Insert the plug P. Connect the plate MM to, 

 say, the positive pole of the source of DC potential and 

 to the top contact of an ordinary two-contact tapping 

 key, K, the tongue of the key being connected to the plate 

 NN. X"ext connect the negative pole of the source of 

 potential to the bottom contact of the key K. These 

 connections are shown in Fig. 1. Then upon depressing 

 the key the full potential of the source is applied across 

 the plates, while upon releasing the key, the potential 

 is removed and the plates are short-circuited together. 

 For ease in observation the space between the plates 

 MM and XX should be strongly illuminated. This may 

 be done by means of a projection lantern, using a hori- 



