ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 



473 



fitted with taps c and c'. The lower cap is also provided with a brass rod, 

 upon which, by means of a screw, can be fastened bits of metal or carbon, h. 

 This is the second electrode. The small 

 cones of birch-wood charcoal are freed as 

 far as possible from foreign bodies by 

 prolonged treatment with acids and alkalis, 

 followed by prolonged boiling. The car- 

 bons can now be used in various ways. 

 If liquid, the carbons are soaked therein. 

 Other matter is first heated in a platinum 

 vessel with dry chlorine gas. The gas 

 with chlorides is then passed through a 

 tube containing some carbons, which be- 

 come impregnated by the substances. 

 Combinations other than chlorides are 

 deposited on the walls of the tube ; these 

 are placed in a hole in the carbon, or in 

 small platinum or aluminium cups soldered 

 to&. 



When the substance to be examined 

 is arranged in the apparatus, the latter is 

 filled with dry hydrogen, and the elec- 

 trodes united with the poles of a battery. 

 When the current is closed the spectrum 

 is observed. 



By this method a thin microlith, • 02 

 mm. by 0*001 mm., observed in a piece of 

 Podolsk quartz, was found to consist of 

 aluminium, beryl, and silicon ; conse- 

 quently the microlith was beryl. 



Copper. — Achromatic Condensers. Engl. Mech., XLV. (1887) p. 300. 



Gill, R. — Camera Lucida. 



[Describes one made of a cover-glass, and cooting the fraction of a penny.] 



Sci.-Gossip, 1887, p. 116. 

 liEACH, W. — The Lantern Microscope. 



[Describes his arrangements for illumination.] 



Engl. Mech., XLV. (1887) pp. 50-1. 

 Terry, W. A. — Notes on Diatom Study. 



[Varnish cell 1/100 in. thick for studying motions of diatoms.] 



Amer. Mon. Micr. Journ., VIII. (1887) pp. 44-6. 

 Tkcester, C. — Hilfsvorrichtung fiir das Mikroskopiren bei Lampenlicht. (Contrivance 

 for use with the Microscope by lamplight.) 



[Plate of blue-tinted glass, one side of which is dull, placed in the aperture of the 

 stage so that the mirror and condenser form an image of the lamp-flame upon 

 the dull surface. This will be found to obviate the two chief objections to the 

 use of lamplight, namely, the colour, and the parallelism of the rays which 

 gives rise to interference phenomena.] 



Zeitschr. f. InstrumentenL, VII. (1887) p. 65. 



(■1) Photomicrograpliy. 



Photographic Apparatus for the Microscope. — The introduction of 

 dry plates has given such an impetus to photomicrography, that in the 

 course of last year we commenced to collect the illustrations for an extended 

 notice of the various forms of photomicrographic apparatus. On reviewing 

 them, however, we fear that many have now scarcely more than an historical 



1887. 2 I 



