606 



Mr. R. T. Beatty on Secondary 



as to lie on the glass plate. With practice the square can 

 be made to lie quite flat. Place another pellet of! wax on 

 top of the square and heat to form another film, so that 

 when cold the square is firmly fixed on the plate. The 

 square can now be cut into strips of any width by a pen- 

 knife, and the edges of these strips will be quite smooth 

 and straight. On heating, a strip can be lifted off the 

 plate on the point of a pin, and as it is lifted the wax 

 solidifies on it and protects it from injury or from being 

 blown about. The strip is now immersed in xylol and then 

 in alcohol, to remove the wax, and is then carefully removed 

 from the liquid on a strip of grease-free paper, all kinks 

 being straightened in the process. It will now dry perfectly 

 flat and is easily detached from the paper. The author has 

 prepared in this manner gold leaves 7 cm. long and *1 mm. 

 wide. 



A leaf of these dimensions was tried in the electroscope, 

 but though it greatly increased the sensitiveness, 1 volt 

 causing a deflexion of 500 divisions, it was found very difficult 

 to eliminate the motion due to air-currents. Even casual 

 air-currents striking the case of the instrument would set up 

 differences of temperature sufficient to cause a disturbing 

 current inside. 



Finally an electroscope was devised in which these dif- 

 ficulties were overcome, and in which the leak due to the 

 natural ionization of the air was eliminated. 



It consisted (fig. 2) of a rectangular brass case with two 



+200 Volts 



Fig. 2. 



TO /OH J Z AT I ON CHAMBER 



200 Volts 



Ssb2 



sliding quadrants Q, which were insulated from the case and 

 connected to voltages of +200 and —200 volts respectively. 

 The gold leaf, 2*5 cm. long and 1 mm. wide, hung between 

 the quadrants, and was initially earthed. By moving the 

 quadrants by means of two short-pitched screws S, the sensi- 

 tiveness of the instrument can be varied. The quadrants are 



