854 SUMSIAEY OF CURRENT RESEARCHES RELATZNGt TO 



same confidence as before tliat they truly picture the surface marking 

 they are supposed to represent." 



Fig. 202. 



mv^t*mmm 



ifittti(n«i«i«i«fii«i»ji 



m^mm^mm^ 



Cohen and Grimm's Microphotographs of Minerals and Rocks* 



— The first four parts of these photographs, illustrating the micro- 

 scopical structure of minerals and rocks, have now been issued. 

 Each part consists of eight plates, with four figures on each plate, 

 ■which have been selected and arranged by E. Cohen. 



The photographs are beautifully executed by J. Grimm. 



Braham's Lamp.t — This is simply a diminutive lime-light with 

 a plano-convex lens in front of it, and with a rack adjustment so as 

 to produce from the small pea of light a divergent, convergent, or 

 parallel beam. It is also fitted to a universal stand so that it can be 

 placed in any desii'ed position relatively to the object. 



The lamp is fed by ordinary coal-gas, the oxygen united with it 

 being pressed through a fine jet from a bladder, sufficient for an 



* E. Cohen and J. Grimm, ' Sammlung von Mikrophotngraphien zur Veran- 

 schaulichung der Mikroskopischen Structur von Mineralien und Gesteinen.' 

 (Stuttgart, 1881.) 



t North. Microscopist, i. (1881) pp. 202-3. 



