ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



103 



fourth lecture also explained the methods of lens-testing adopted at Kew 

 Observatory and the official certificate issued. The lecturer referred to 

 the following authorities as useful sources of information : Winkelmann's 

 Himdbuch der Physik; Muller Pouillet's Lehrbuch der Physik) M. von 

 Rohr's Theorie des Photographischen Object ivs ; Hovestadt's Jenaer 

 (Has; Silvanus Thompson's translation of Lummefs Photographic 

 Optics ; and Dallmeyer's Telephotography. 



Molisch's New Freezing Apparatus.* — This (fig. 27) is intended 

 for exhibiting objects under the Microscope in laboratories. It is said 



Fig. 27. 



to be adapted for a constant temperature of — 10° C. A window admits 

 light on to the mirror, and the various adjustments are effected by rods 

 actuated from the exterior. 



Dongier, R. — Apparat zur Messung der Krummung und anderer Constanten ernes 

 Optischen Systems. Zfiit. /. Instrument!:., XXI. (1901) p. 36'2. 



Kohst, R. — Ueber mikroskopischen Electricitatnachweis. 



[The author reviews the limits of delicacy of the methods of electrical 



reactions observable by microscopic methods. He especially emphasises 



the electrolytic reactions when coloured or crystalline products are 



formed.] Zeit.f. wise. Mikr., XVIII. pp. 427-311. 



Stkehl, K. — Plaudereien uber Optische Abbildung— Mikroskopie ; Spektroskopie. 



[Conclusion of a series of articles.] 



Central-Zeit. f. Opt. u. Meeh., XXIII. (1902) pp. 193-4. 

 "W a l l e k a n t, F. — Sur un nouveau modele de refractometre. 



Bull, de la Soc. Fran?, de Miner alog., XXV. (1902) p. 54. 



* Zeitschr. angew. Mikr., viii. (1902) pp. 33-4 (1 fig.). 



