491 
THE CONSTRUCTION OF A RUTHERFORD’S ELECTROSCOPE. 
EDWIN MorRISoN. 
INTRODUCTION, 
At the suggestion of Dr. R. A. Millikan the author recently undertook 
the problem of constructing an electroscope for general laboratory work in 
radio-active measurements. The general outlines and plans suggested 
by Dr. Rutherford in his originai papers published in the Philosophical 
Magazine and in his work entitled Radio-active Transformations have 
been followed. Suggestions have also been taken from the following works: 
Studies in Radio-activity, by Bragg; Conduction of Electricity Through 
Gases and Radio-activity, by McClung; and Practical Measurements in 
Radio-activity, by Makower and Geiger. 
The purposes have been, first, to show, in greater details than the 
original papers give, the methods of constructing a successful electroscope ; 
and, second, to embody in one instrument as wide a range of experimental 
work as possible. 
CONSTRUCTION. 
A diagram of the electroscope is shown in Fig. 1. The dimensions of 
the gold leaf chamber (FE) are 10x10x10cm. This chamber is con- 
structed from sheet brass 1.7 mm. in thickness. The four plates for the 
sides, top and bottom are first carefully jointed by means of a file and 
then soldered together as shown in Fig. 2 (A). To facilitate the process 
of soldering two right angle pieces of metal are joined together forming 
a right angle frame as shown in Fig. 2 (B). When two pieces of the box 
are to be joined together they are carefully adjusted upon the frame, a 
few small pieces of solder and soldering fluid are placed along the joint 
and a ‘pointed flame is directed along the joint in the inside angle until 
the solder is thoroughly fused. In this way the parts of the electroscope 
box can be joined together square and straight. 
The front side of the electroscope box is a hinged door. This door has 
a window in it 6.5 cm. square covered with mica. Through this window 
the gold leaf may be observed by means of a reading microscope. A dia- 
