ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
863 
for further investigation. The diameter of the revolving plate is only 
limited by the construction of the Microscope-stand, to which it is an 
adjunct.” 
Fig. 94. 
Heating Apparatus for Crystallographic Optical Work.* — Herr 
R. Ruess describes three forms of heating apparatus which serve for 
the optical examination of crystals at high temperatures. 
The first apparatus, represented in fig. 95, is intended for tempera- 
tures up to 450°, which can be measured by a mercury thermometer. It 
consists of a box formed of a bent brass tube, of rectangular section, 
through which a stream of hot air is led. The arm A' which rests upon 
the stage of the Microscope serves as air-bath for the crystal under 
examination, while the other, directed upwards, acts as a chimney 
through which the heated gases escape. 
* Neues Jahrb. f. Min., Beilage Bd. vii. (1890) pp. 406-16. 
