Physics. — "A neio Electrometer, specially arranged /or radio-active 

 Investigations" . Part II. Bj Miss H. J. Folmer. (Coiniiiunicated 

 by Prof. H. Haga). 



m^ 



(Communicated in the meeting of September 2U, 1917.) 



In Part I, communicated bj Piof. H. Haga in the meeting of 

 May 30 1914, the following brief description was given of the elec- 

 trometer which is represented in figure 1 and reproduced here 

 once more : 



The apparatus consists of two 

 separate spaces, viz : the measur- 

 ing space c\ a brass cylinder of 

 small height, and the ionisation 

 space proper/; a brass cylinder 

 of volume 1 litre; the two cylin- 

 ders are insulated from each other 

 by ebonite. 



In the measuring space c is 

 the metal needle h, supported in 

 the middle by a second needle 

 d, insulated by amber; b -\- d 

 together form the conductor, 

 which is charged by the ionisa- 

 tion current. 



In c is also found the very 



thin aluminium strip <'/, which a 



few mm. above b is fastened to 



a thin metal rod with mirror, 



^'ë- 1- suspended on a Wollaston wire, 



which is fastened to a torsion head insulated by means of ebonite. 



Through a perforation in the amber and in the ebonite a rod /can 



be brought in contact with the needle d. 



In this way, a, b -\- d, c and ƒ can therefore be separately brought 

 in a conductive connection with a storage battery or with the earth ; 

 r rests on a brass bottom plate to which legs are fastened which 



