ZOOLOaY AND BOTANY, MICROSCOPY, ETC. 



87] 



able to avoid the inconvenience alluded to ; for it is quite possible to 

 place the electrodes in close proximity with the preparation which is 

 on the inner side of the cover, and to examine it in consequence with 

 high powers. I attach to each side of the slide a strip of tin-foill 

 which passes over the putty and reaches its inner side (s 8, fig. 199). 



Fig. 199. 



J,'^^:. 



=«^r 



Cemented to the cover are also two small strips of tin-foil s' s', which 

 running in the axis of the cover, leave between them a space of a few 

 millimetres in diameter. The object is placed at this spot, and the 

 cover is so disposed on the wall of putty that the metallic strips of 

 the cover lie on the strips covering the putty, and the cover is then 

 firmly pressed down on the soft putty. The cell being now complete, 

 the electric current is conducted by the strips of metal to the object, 

 through which it passes at the same time ; this lies immediately 

 beneath the cover, and can therefore be examined with the highest 

 powers. It is, moreover, no small advantage to combine the appli- 

 cation of electricity with researches on the influence of gas, because 

 we can neutralize or aid the effects of the current by the introduction 

 of different gases." 



Eartiiujs * (fig. 200) is a glass slip ah c d, about 100 or 120 mm. 

 long and 30 mm. wide, to which are attached by starch paste two 

 pieces of somewhat narrower tin-foil A and B, with a space between 

 them of about 25 or 30 mm. The tin-foil projects beyond the ends 

 of the slip as shown in the figure. Over the tin-foil two thick cover- 



FiG. 200. 



h i "h 



glasses d ef g and Ji ihl arc cemented by marine glue or a mixture 

 of pitch or rosin for the stage clips to rest upon. The jjlatinum 

 wires n and j) arc loose, and are bent in the form shown at C. The 

 part m r B re sts on the tin-foil and the other curved portion m t v 

 dips into the fluid in the cell D. They can be brought close together 

 if required. If they are to bo used for covered objects they must 

 be bent so as to lie horizontally and be as thin as possible: the 



Frey 



• Harting, op. cit., ii. pp. 145-6 (1 fig.)- Dippel, op. cit., pp. 6.57-8 (1 

 :y, H., ' DaH MikroHkop," &c. Transl. by Cutter, 1880, p. 102 (1 flg.). 



^ 3 L 2 



:•)• 



