124 



SUMMAEY OF CUREENT RESEARCHES RELATING TO 



circumference of a heavy brass disc. Over the disc fits a ring 

 (shown separated in the fig.), which when screwed down fixes the feet 



Fig. 6. 



Fig. 7. 



\ 



of the tripod immovably. In the 

 centre of the disc is a support for 

 the end of the standard to rest on. 



The feet fold together, and the 



mirror and stage can be turned up 



against the standard, whilst the 



horizontal arm can be set vertical. 



When the body-tube is unscrewed, 



the whole instrument is reduced to 



very small dimensions. For a coarse 



adjustment the stage is moved, and 



for a fine adjustment the draw-tube, 



in which the eye-piece slides. Both movements are by rack and pinion. 



Klein's Horizontal Heating Microscope.* — This (fig. 8) was 



devised by Prof. C. Klein for the purpose of observing minerals with 



the Microscope under high temperatures. 



The body-tube is mounted horizontally on a brass standard screwed 

 to a metal plate, with which the wooden base is strengthened. 

 Opposite to it is a second standard, which slides in grooves and 

 carries the lower part of the Microscope — mirror, condenser of long 

 focus, and polarizer. In another groove at the side of, and parallel to 

 the former, is a third standard, with an extending rod, which supports 

 a pair of forceps with platinum points to hold the mineral to be ex- 

 amined, which can be placed at any convenient point between the 

 condenser and the low-power objective. An analyser is attached by 

 a hinge-joint to the front of the eye-piece, so that it can be turned up 

 out of the way when not required, as shown in the fig. A selenite 

 plate can be interposed between the analyser and the eye-piece. A 

 screen (shown by dotted lines) can be placed on the lower tube to 

 shut off extraneous light. 



Heat is applied to the object by a Bunsen burner, which is 

 movable on a hinge, so that the flame can be quickly applied to a 

 given point and as quickly removed again. 



* Nachr. K. Gcsell. Wiss. Gottingen, 1884, pp. 133-5. 



