1896.] and Rontgens X Rays. 61 



I also tried without success to photograph in this way by the 

 phosphorescence excited in a screen powdered over with luminous 

 paint, by the sparks passing between the terminals of a Ruhmkorff 

 coil placed close to the screen. 



It would thus appear that we can have vivid phosphorescence 

 without any production of these rays. 



I next tried whether the negative electrode could excite these 

 rays without the aid of the walls of the tube. To test this, I 

 cut a piece off a photographic plate and enclosed it in a small 

 ebonite box in the tube in such a way that it came between 

 the negative electrode and the glass ; in this case the plate was not 

 affected. 



The next experiment I tried was designed to try if any evidence 

 as to the transverse or longitudinal nature of these rays could 

 be obtained by comparing the depth of the shadows cast by two 

 plates of tourmaline, (1) when the axes were crossed, (2) when 

 the axes were parallel. Two pairs of plates A and B were used 

 and a series of photographs were taken ; in some the axes of 

 A crossed, and those of B parallel, while in others the axes of 

 A were parallel and those of B were crossed. A very considerable 

 number of photographs were taken, but there was no evidence 

 of any effect being produced by the relative position of the 

 axes. 



A series of experiments (which were not completed until 

 Jan. 29, the day after the paper was read) were made to test 

 whether a charged electrified plate would retain its charge of 

 electricity when exposed to these rays: it was found that the inci- 

 dence of these rays produced a rapid discharge of the electricity 

 from the plate, whether this was charged with positive or negative 

 electricity ; the rate of leak was independent of the sign of the 

 charge. The potential difference used in these experiments was 

 about 200 volts. An uncharged metallic plate when exposed to 

 these rays was not sensibly electrified. 



I have much pleasure in thanking Mr Everett and Mr Hayles 

 for the assistance they have given me in these experiments. 



(2) The Equilibrium of Isotropic Elastic Solid Shells of 

 nearly Spherical form. By C. Chree, Sc.D. 



The equations of equilibrium for isotropic elasticity can be 

 solved approximately in cases where the surface is not exactly but 

 only nearly spherical by a method which I have applied in the 

 American Journal of Mathematics, Vol. 16, pp. 299 et seq. In all 

 the problems solved in the paper referred to, the material was 

 bounded by a single surface, but it was indicated I. c. p. 382, how 

 the method could be applied to a shell. The present paper deals 



