THE STKUCrUKE OF THE NUCLEUS. 



95 



S, to be examined. A definite volume, say 500 euU. cm., is necessary. The receiver 

 has two outlets provided with stojj-cocks, and a third, g, leading to the vacuum 

 gauge. The outlet leading to F is the filtering arrangement; the outlet, F, e, is 

 the avenue of sudden exhaustion, and therefore made of wide tubing, say 1 cm. in 

 diameter. 



oz 



9 



Fu;. I,— Condensation CuAMniiR. R ; Exiiausiion Resf.rvoik, B, and Appuktenances. Scale J. 

 Fu;. 2. — Lamp, Receiver, and Goniometer. Diagram. 



The auxiliary flask, B, of about l/;5 the capacity of RA, is a resei'voir for air at 

 low pressure. It communicates with tlie jet pump (through a desiccator, if neces- 

 sary) by the pipep, with R through E, and with tlie external atmosphere for the 

 adjustment of pressui-e, I»y the pipe a. The attached vacuum gauge is shown at g'. 



Figure 2 is a plan in diagram of the a[)i)aratus for viewing and measuring the 

 coronas, R being the receiver, G the goniometer, and L the source of light, at 

 distances, respectively, 1 and 3 meters (not shown in figure) from the center of the 

 receiver. The eye is at E. Under these conditions the coronas may be measured 

 in a darkened room with facility, though, of course, from the absence of sharp lines, 

 not with great accuracy. The goniometer is of the kind desci'ibed in § 2, Chapter 

 III, needle points at n v.' being adjusted and their distance apart pi'icked in papei'. 



The method of work requires that R should be first freed from nuclei, by 

 precipitation or aspiration, combined with filtration in the usual ^vay, until the 

 degree of exhaustion selected for the experiments is no longer accompanied by even 



