626 SUMMARY OF CURRENT RESEARCHES RELATING TO 



MICROSCOPY. 



A. Instruments. Accessories, &c* 

 (1) Stands. 



Deschamps' Simplified and Improved Solar Microscope.f — The 

 simplification depends primarily on the working of the movable mirror, 

 which is moved without pinions or engaging gear by means of a vane and 

 a wire. The vane produces the left-to-right (or contrary) motion ; the 

 wire attached to the top of the mirror raises or lowers it, and, being set 

 in a caoutchouc disc, enclosed in a small copper cylinder, can be regu- 

 lated with extreme nicety. By the help of this system the most inexperi- 

 enced operator is, after a few minutes' practice, a perfect master of the 

 direction of the solar beam which he easily controls and directs upon 

 any desired point of the screen. The objective is, moreover, adjusted 

 without a micrometric screw, and the diaphragm is fixed to the objective 

 without forming a separate piece. All the movable parts are carried on 

 a single guide-bar on which they slide, or are fixed by means of clamp 

 screws. 



The improvement secures the elimination of injurious heat, and this 

 elimination is secured by a simple arrangement of lenses, and without a 

 trough of water or alum. 



■ The condenser is first selected of diameter sufficient for light, with- 

 out accumulating a harmful excess of heat. The focus is replaced by a 

 system of two non-achromatic lenses of equal focal length and separated 

 from each other by the same distance. This system is situated in rela- 

 tion to the condenser at a point such that there is formed, in the first 

 place, not an exact focus to which the rays converge, but an elongated 

 focus at no point of which the luminous beams entirely converge. In the 

 second place there is produced (and this is the chief cause of elimination) 

 an effect of dispersion and of partial recomposition ; the aggregation of 

 lenses doing the work of a prism, and, as the rays of the infra-red (heat 

 rays) are the less refrangible, they are kept in the periphery, and there- 

 fore removed from the line of the object, which is placed outside the 

 violet cone in a spot where white light is recomposed slightly tinted 

 with blue, green, or yellow, colours which diminish neither the inten- 

 sity nor the brilliancy. 



A living animalcule can be examined and studied at leisure without 

 losing life or sensibly suffering. The magnification exceeds 1500 dia- 

 meters without loss of clearness, so perfectly achromatic are the lenses of 

 the objectives. 



The results obtained by this instrument are inferior in no respect, 

 from the point of view of perfection of the images, to those given by the 

 best apparatus hitherto in use. 



Deschamps' Telemicroscope.* — The telemicroscope is so called be- 

 cause, whilst loupes magnify three or four times at 1 cm. distance, and it 



* 



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

 minating and other Apparatus; (4) Photomicrography; (5) Microscopical Optics 

 and Manipulation ; (6) Miscellaneous. 



t Comptes Kendus, cxxx. (1900) pp. 1175-6. $ Tom. cit., pp. 1176-7. 



