I. MICROSCOPES. 771 



3575. Microscope constructed specially for the examination 

 of microscopic sections. R. Fuess, Berlin. 



3576. Immersion Lens, with special contrivance for in- 

 creasing the magnifying power from 300 to 1,000 times with the 

 low eye-piece. R. Winkel> Gottingen. 



3577. Microscope (small model), commonly used. 



Dr. Hartnack, Potsdam. 



3578. Small Microscope, specially suited for mineralogical 

 researches. Dr. Hartnack, Potsdam. 



3579. Large Microscope. Dr. Hartnack> Potsdam. 



These instruments are sufficiently well known, and it is not necessary to 

 bring forward their peculiarities, but the mineralogical microscope has been 

 recently constructed, and the exhibitor requests mineralogists to direct their 

 attention to it. 



3579a. New Dissecting Microscope with three achromatic 

 powers, support for arms, and rack focussing giving three move- 

 ments. Harvey, Reynolds, and Co.. 



3580. Microscope for Dissecting, with pincers and plate 

 for dissection, and simple Microscope with rod action. 



Geneva Association for Constructing Scientific Instru- 

 ments. 



The Geneva Association constructs three different models of microscopes. 

 In the plainest model the focussing movement is worked direct by the hand 

 acting upon a rod which supports the optical system, and which slides up and 

 down through a groove. The light is given by a mirror placed below the 

 stage. The instrument is enclosed in a box. In the second model the focus- 

 sing is effected by means of a rack. Lastly, in the third model, the most 

 complete of all, a pair of pincers revolving around two rectangular supports 

 are substituted for the plate. With the help of this addition an object placed 

 at the extremity of the pincers can be successively examined on all sides, and 

 without leaving the focus of the glass. The sighting is the same as in the 

 preceding model. 



The optical system of each of these microscopes is composed of three 

 " Wollaston " doublets with inner diaphragms, of 1 inch, ^ inch, and \ inch 

 focal distance, giving magnifying powers of 9, 18, and 36 times, for 25 cm. 

 length of vision. 



The Geneva Association supplies besides to those who require higher 

 powers achromatic lenses with short focus, giving great clearness and light. 

 An achromatic lens of 2 millimetre focus produces a magnifying' power of 125 

 times with perfect clearness. 



3581. Large Microscope, with Reversing Action, and 



cylindrical pincers for objectives. 



Geneva Association for Constructing Scientific Listnc- 

 ments. 



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