ZOOLOGY AND BOTANY, MIOROSOOPY, BTO. 



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examining other objects, especially if they have glass covers, the 

 direct illumination of course causes much reflection from the glass, 

 and makes the object look milky. The reflection from iron and steel, 

 however, entirely overpowers this light from the cover, so that it 

 does not interfere with the use of the illuminator." (See also infra, 

 p. 175, for Dr. Sorby's paper on the preparation and illumination of 

 iron and steel for microscopical examination.) 



Equalizing the Thickness of Slips with Oil-Immersion Con- 

 densers.* — It is necessary that an oil-immersion condenser should 

 have a fairly long focus ; otherwise it would be of no use if the slip 

 happened to be rather thick. If the slide is thin, it will be found 

 impossible to keep the oil contact when the condenser is in focus, 

 unless you increase the thickness 

 of the slide, by uniting a thick F[q, 15. 

 cover-glass to the back by oil. 

 It will be found very difficult to 

 do this without oiling the stage 

 when the Microscope is inclined. 

 The oil between the condenser 

 and the cover-glass is sure to 

 unite with that between the cover- 

 glass and slide, and then the 

 cover-glass falls, upsetting the 

 whole arrangement. To obviate 

 this Mr. E. M. Nelson has found the following plan to answer 

 admirably. A piece of glass 1 in. square, upon one side of which, 

 close to one edge, a strip 1/8 in. broad is fastened by shellac, ia 

 oiled to the back of the slide ; the ledge hooking over the edge of the 

 slide prevents it slipping down. 



Coxeter's Silico-Carbon Battery and Electric Lamp. — Messrs. 

 Coxeter and Nehmer exhibited at the January meeting the battery 

 and illuminator, figs. 17 and 18. 



The battery has in each of the four cells two large silico-carbons, 

 with platinum clamp connections, and one zinc rod with screw 

 terminal. It is charged with chloride of ammonium. No chemical 

 action takes place except when it is actually in use ; and once charged 

 it needs no further attention, but is always ready when required. 

 There is a shunt on the lid to connect the cells consecutively, and thus 

 illuminate the object with the varied requirements of high and low 

 power. The current passes through a rheostat before it reaches the 

 incandescence lamp, to prevent its being spoiled ; the electrical 

 resistance should be afterwards lessened or taken out of the circuit 

 by moving the sliding button A, and thus the battery is economized. 

 The lamp-holder is jointed, and can be moved into any position, 

 either above or below the stage, or to any part of it, and the position 

 of the light is not altered by any movement of the Microscope. The 

 light can be turned on and off at the lamp when desired. It is 



* Engl. Mech., xlii. (1885) p. 280 (3 figs.). 



K 2 



