ZOOLOGY ANL BOTANY, MICROSCOPY, ETC. 



615 



air is supplied under pressure, and by combination of tlie gas-burner and 

 air-supply, any desired temperature can be maintained for a long time in 

 the centre of the field. 



Zeiss Heat-Microscopes.* — Figs. 92, 93, 94, show various forms of 

 these instruments. Fig. 93 is Lehmann's Crystallisation Microscope 



Fig. 92. 



Fig. 93. 



arranged for subjective observation at high temperatures. Fig. 92 

 is a new Physico-Chemical Microscope for subjective observation and 

 projection at high temperatures (900° C.) fitted with a gas-heat con- 

 denser, an air-cooling arrangement, and a polarising apparatus. 



* Special Catalogue, Carl Zeiss (Jena) 1906. 



