THE MICBOSCOPE 9 



the direction and the angle of incidence of the light when 

 illumination of opaque objects is desired. 



The following illustrations of microscopes are chosen to 

 indicate the various types that are at present being made by 

 the leading manufacturers in England and on the Continent. 

 They are not selected as being necessarily the only types 

 suitable for the purpose in view. It may be taken as certain 

 in purchasing a microscope that the best will be found in every 

 way the most satisfactory, although it need not be implied 

 that an expensive stand is a necessity. There are few really 

 bad microscopes made nowadays ; even the low-priced ones, 

 as the result of competition, have to be well finished, and, if 

 bought from a maker of repute, will almost invariably give 

 satisfaction. 



The instrument selected will largely depend on the work 

 that has to be done. If high power, and work of a critical 

 nature is required, then an instrument of the very highest 

 class is essential ; but for ordinary work there are many micro- 

 scopes of moderate price available. The writer used for some 

 thirteen years, without interruption, a microscope of the Wales 

 type, made by Messrs. Swift & Son (Fig. 1), and has found 

 it in every respect satisfactory. It was first adopted because 

 of its being so highly recommended by that pioneer of photo - 

 micrographic work, Mr. Andrew Pringle, who referred to it 

 particularly in the earliest editions of his book on photo-micro- 

 graphy. As the writer has found this microscope equal to 

 almost any requirement, he feels justified in giving some 

 special description of it, for it will meet the needs of the 

 majority of photo-micro graphers. 



The chief advantage of this form. of stand is that the centre 

 of gravity of the instrument is practically constant whatever 

 the inclination at which it may be used. As will be seen by 

 the illustration the inclination of the body is effected not by 

 swinging on a central pivot, but by the movement of a semi- 

 circular portion of the body part between two jaws, and these 

 can be clamped by a clamping-screw so that the microscope 

 is rigid in any position. The base of the stand has a good 

 wide spread, so that the instrument is stable and well balanced ; 

 the fine and coarse adjustments are entirely satisfactory, and 

 have worked with precision under the most trying circumstances. 



