PRODUCED IN GASES BY RONTGEN RAYS. 
197 
the width of the juncture Jc will be considered later. The apparatus as used will now 
be described. 
§ 3. The Apparatus. 
The main parts of the apparatus are represented in fig. 2, where the lower part of 
the figure is a vertical section, while the electrical connections in the upper part are 
viewed from above. 
The outer cylinder, A A', had an internal diameter of 5*11 centims., and a total 
length of 142 centims. For convenience the length is shortened in the figure by the 
omission of two sections. The part to the left of V, 41 centims. long, and the part 
to the right of V', 81 centims. long, were made of strong brass tubing. The portion 
DD' between these was 20 centims. long, and consisted of an aluminium tube, which 
was of the same internal diameter as the brass cylinders. Brass collars over the ends 
of the aluminium tube fitted into the external collars V and V soldered to the brass 
cylinders, and so formed close-fitting joints that were made gas-tight by sealing them 
on the outside. The whole cylinder was supported on a board, XX , and insulated by 
means of four paraffin blocks, two of which are represented by P and Pi 
The inner cylinder, BBj was an aluminium tube 1 centim. in diameter, closed at its 
ends by conical pieces. At C the cylinder was divided so that the two portions were 
held one-half of a millimetre apart and insulated, by means of an ebonite plug. At 
the end, B', the tube was supported and kept central by means of two small ebonite 
rods, Q. The tube was further supported by the two stiff brass wires, Y and Y , 
which lead through the ebonite plugs, R and R , in the outer cylinder, and served to 
