I. MICROSCOPES. 915 



bright. The field of view is very large, the two axes of the white topaz are 

 seen. Compensation can be effected with a parallel or a perpendicular 

 quartz. 



35S9b. Polarising Microscope on round foot. 



L. Laurent, Paris. 



Same model, but mounted knee-wise, upon a pillar wich lengthening piece, 

 and a tripod. This model can be placed horizontally and is then used for 

 measuring the divergence of the axes of crystals, immersed in oil, heated, &c. 

 For this purpose the small glasses at the objective and at the illuminator are 

 removed, they are mounted so as to travel easily. The glass support is 

 also removed and replaced by the tube that contains a Nicol. The distance 

 between the two plates of the glasses of the objective and of the illuminator 

 is 15 millimetres, which allows room for either an oil pan or a stove by 

 means of a support bearing a divided dial (which is not exhibited). The 

 principle is that of M. Des Cloizeaux, and the arrangement, especially for 

 this last model, is due to the exhibitor. 



3589c. Early Microscope. John Waugli. 



3589d. Two Microscopes in cases. 



W. Techner, 180, Fried-rich Strasse, Berlin, W. 



Polarising Microscope for projection. 



L. Laurent, Paris. 

 Glass Sunk Cells for the microscope (4). 



L. Laurent, Paris. 



3590. Solar Microscope, with alum cell. Laurent. 



Model, prepared for projections, at the request of M. Des Cloizeaux. 

 It has already been used at the Sorboune and at the Paris Museum. 



The field of view has been made as large as practice allows, with especial 

 regard to illumination. The gypsum and its variations through heat can be 

 clearly seen. By the advice of M. Des Cloizeaux, the horizontal pincers 

 have been replaced by vertical ones which are much more handy. An alum 

 pan for stopping the greater part of the heat has also been added to the pro- 

 jection lantern, and it has then been possible to project platinocyanure of 

 barium, and formiate of copper, without altering them. 



3590a. Dr. Lionel Beale's Portable Microscope, for 



class purposes or for travelling. Thomas Hawksley> 



(c.) ACCESSORY APPARATUS. 



3591. Photographic Apparatus for the Microscope. 



Seibert and Krafft, Wetzlar. 



This apparatus can be connected to any microscope, which, for this pur- 

 pose, is placed perpendicularly under the box in front of the apparatus, 

 after which, in order to exclude unsuitable light, the cloth-bag, fitting 

 tightly by means of a gutta-percha ring, is pulled over the tube. The adjust- 

 ment of the picture is effected by means of the glass-plate contained in the 

 box, which is provided with squares and the ocular -like microscope. The 

 lines of the glass-plate must be placed downwards. The microscope is placed 



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