ZOOLOGY AND BOTANY, MICROSCOPE, ETC. 



671 



the whole surface can quickly or slowly be systematically explored. 

 The movements are controlled by the left hand of the operator, his 



Fig. \5'i 



right being then free for the micrometer screw. The apparatus is thus 

 especially suitable for the examination of a series of sections. 



(3) Illuminating- and other Apparatus. 



Colour Illumination of Microscopic Objects.* — S. E. Dowdy de- 

 scribes a simple procedure for making coloured gelatin discs for illu- 

 minating objects by Rheinberg's method .t First of all, obtain an 

 ounce of good quality clear gelatin. Shred this up into small pieces 

 and cover them with 4 oz. of water, and allow it to stand till quite 

 soft ; then add another 2 oz. of water," and warm gently on a water- 

 bath (a saucepan containing a little water will do) until the gelatin 

 dissolves. This will constitute our stock solution, which may be 

 coloured as follows : — -Procure half a dozen of the penny packets of 

 anilin dyes, selecting brilliant contrast colours. Add about four grains 



* English Mechanic, lxxvii. (1903) p. 324. 

 t See this Journal, 1893, p. 373; 1899, p. 142. 



2x2 



