230 SUMMARY OF CURRENT RESEARCHES RELATING TO 



MICROSCOPY. 



A. Instruments, Accessoi-ies, etc.* 

 (1) Stands. 



Genevan Universal Microscope for Mineralog-ical Researches.! — 

 This type of Microscope (iigs. 8, 9, 10) has been designed to afford a 

 means of making on the same instrument observations the most diverse. 

 At the same time the stand is of a very complete construction, and its 

 adjustments so rigorous as to give an observer entire confidence in his 

 results. The Microscope can be used with the system of permanent 

 centring, or of optional centring. In the former case the objective 

 becomes an adjunct of the stage, and in this form the instrument will 

 adapt itself very conveniently to researches in polarized light on the 

 constitution and properties of minerals. In the system of optional 

 centring the objective becomes an adjunct of the tube, and the Micro- 

 scope can be easily changed into this form from the other without the 

 removal of even a single screw. In the optional form the instrument 

 would be used for all researches requiring Fedorow's methods, as well 

 as for those requiring long-frontal distances ; for such classes of obser- 

 vations, its completely rotating stage, and the facility of adjusting the 

 stage-level, render it particularly convenient. 



When used with permanent centring (fig. 8), the objective becomes 

 a part of the stage, and the Bertrand lens, V, is placed at the lower 

 extremity of the tube by means of the forceps p. The objective is 

 maintained by the usual pinch-grip on the slide-arm c, which itself is 

 connected by the screw with the slide-block C. The milled head B 

 controls the coarse-adjustments of the objective, and the fine-adjust- 

 ments are performed by the screw h with its graduated drum. The 

 construction of the arrangement for measuring ^thicknesses automa- 

 tically overcomes all play of the screw, and the use of the double 

 slide-block C,c^ protects the micrometric screw from over-rapid use. 

 The complete object-carrier can, by means of the knob d mounted on a 

 large looped helix, be rapidly applied to the stage or removed therefrom. 



¥ 



* This subdivision contains (1) Stands : (2) Eye-pieces and Objectives ; (3) 

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

 Optics and Manipulation ; (6) Miscellaneous. 



t Soci6te Genevoise pour la construction d'instruments de physique et de 

 m^canique. Geneve. Special pamphlet, 8 pp. 



