306 SUMMARY OF CURRENT RESEARCHES RELATING TO 



MICROSCOPY. 



A. Instruments, Accessories, etc.* 

 (1) Stands. 



New Heat Microscope.f — This instrument, designed by C. Doelter, 

 is intended for the photography of melting and crystallising processes 

 and for observation in various gases. The heating is electrical, as 

 gas-heating is not sufficiently constant ; the Microscope can be used 

 for ordinary purposes if the heating chamber be removed and a special 

 tube substituted. The instrument is meant to be more particularly 

 applicable to : — 1. Examinations of crystal plates, slides, etc., at tem- 

 peratures not exceeding 1000° C, and in which polarised light should be 

 serviceable. 2. Examinations of melting and crystallising processes up 

 to about 1000° C, especially to the determination of melting points, 

 solidification and reversal points ; in these cases polarised light could 

 be usefully applied up to about 1200° C. The principal distinction 

 between these two classes is that sunlight or some strong artificial 

 light (arc light) is used for the first ; and that, for the second, 

 the light from the incandescent chamber or object acts as the light- 

 source. Even at temperatures from 700° to 1000° C. the incandescence 

 might be used as a light-source, especially if the magnification required 

 is not high. An electric arc-lamp with continuous current and auto- 

 matic carbon regulators is used for the heating. The polariser is a nicol, 

 set as is usual in mineralogical Microscopes. The stage is rotatory and 

 has a circular form. In addition to an adjustable nicol the tube con- 

 tains an upper rotatory nicol, and the ordinary gypsum or quartz wedges 

 can be inserted. The stage is adjustable by means of two screws and 

 the tube for centring purposes is also fitted with two screws. The tube 

 is extensible for attaining higher magnification, and there is an insertion 

 for replacing the stove (or heating chamber) by one of another size. 

 The low and high temperature stoves have heights of 55 and 100 mm. 

 respectively, with inner clear spaces of 12 and 10 mm. broad. The 

 object-holder takes the form of a small platinum tripod or ring ; for 

 melting and crystallising observations a small quartz glass plate is used. 



The interior of the stove is asbestos lined, and special pains are taken 

 to exclude air currents, the top and bottom of the stove being protected 

 with close fitting quartz glass plates. The electric current is taken from 

 the domestic supply, or from a small battery of accumulators. The 

 currents have respectively 3 amperes and 80 volts, and 5 amperes and 

 120 volts. Regulating is accomplished by suitable resistance methods, 

 of which the author gives full particulars. The objective is made of 



* This sub-division contains (1) Stands ; (2) Eye-pieces and Objectives ; (3) 

 Illuminating and other Apparatus ; (4) Photomicrography ; (5) Microscopical 

 Optics and Manipulation ; (6) Miscellaneous. 



t SB. k. Akad. wiss. Wien., cxviii. (1909) pp. 489-9 (3 figs.). 



