240 A. W. Wright — Cathode Hays and their Effects. 



side was crumpled by the tight cover. The aluminium sphere 

 appears diminished in size by the passage of the rays more 

 freely through the lesser thickness of its periphery, and leaves 

 a lighter trace upon the plate than the two others, which are 

 practically opaque, and nearly alike. On either side of the 

 box was a medal of aluminium, the head in one being upper- 

 most, in the other beneath, the two being alike except 

 in position. The medal is one made by Johnson Matthey & Co., 

 some years ago, and one side, the reverse, bears the name 

 of the firm, and the address, Hatton Garden, around the 

 rim. Across the middle of the face is the word Refiners. 

 On the obverse is the bust of Queen Victoria, and around the rim 

 the words Victoria Queen. The raised rim is serrated on 

 the inside on the obverse, but is plain on the reverse. In 

 the cathode picture, owing to the great permeability of the 

 metal, the designs and letters upon both sides are shown, 

 appearing as a similar medal in translucent wax would, if 

 viewed by transmitted light. In the negative the separate 

 letters can be distinguished, and two dots separating the name 

 from the address, though the letters are hardly clear enough to 

 enable one unacquainted with their import to make out the 

 inscriptions. The gradations of light and shade in the nega- 

 tive are too delicate to be represented adequately in any pro- 

 cess print, but are fairly well shown in the wood-cut. The 

 position of each medal can be determined from the greater 

 distinctness of that side which was nearest the photographic 

 plate. 



The plate, VI, represents a portion of a picture obtained Feb. 

 1. The handles of the saw and awl are of cherry wood. This 

 appears very transparent, but gives a shading proportional to 

 the thickness of the wood. The tang of the awl is clearly 

 seen, and that of the saw also, extending entirely through the 

 wooden handle, and expanded or riveted at the end to pre- 

 vent it from being pulled out in use. The eye-glasses in their 

 leathern case show minute details of form, and the varying 

 thickness of the lenses is indicated by corresponding depth of 

 shade. The same effect is shown still more strikingly by the 

 figure of the pocket lens in its ebonite mounting, where no 

 effect of refraction can be traced, the lenses simply showing 

 the greater thickness at the center by the deeper shading. 

 The sides of thin ebonite are separated by thicker pieces of 

 the same material at the ends, and are held together by two 

 brass rivets which are plainly depicted. 



With a view to study the character of the rays outside of 

 the vacuum-tube the following experiments were made: A 

 flat, rectangular plate of copper, l-8 mm in thickness, 25*5 cm 

 long, and 21'5 em wide was used, and in the center of this two 

 straight, parallel slits l-5 mm wide and 35 mm long were cut 



