ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



101 



that described in the next section, and it was found that a period of 

 three minutes was quite sufficient to take a stereogram, including the 

 necessary adjustment of light, slides, &c. If the stereogram is required 

 to produce the impression of vision from above, the horizontal must be 

 so arranged that the true place of the lamp is the apparent position of 

 the observer. A lamp should be chosen the length of whose filament 

 is a third of the diameter of the aperture of the objective ; the filament 

 should be inclined lengthwise, at an angle of 45° to the horizontal. 



Improvements in the Vertical Microphotographic Camera.* — W. 

 Scheffer describes (fig. 26) an arrangement by which a Microscope can 

 be used in the ordinary way, and yet almost instantaneously adapted 

 for use with a vertical camera. The 

 spacious foot-plate has two adjust- 

 able bars, which are secured by bind- 

 ing-screws, and serve for putting the 

 Microscope into the exact position for 

 accurate centring with the camera. 

 A strong pillar is at the further end 

 of the foot-plate. In the upper and 

 perforated end of this pillar is a steel 

 rod carrying the camera, and rotatory 

 about its axis ; it is notched for the 

 adjustment over the Microscope, and 

 is firmly clamped in this position by 

 a screw. This arrangement secures 

 the accurate adjustment of camera 

 and Microscope. The rod not only 

 bears sleeves with suitable arms for 

 the camera, but is graduated so that 

 the position of the ground-glass 

 screen may be accurately controlled. 

 The flame is so arranged that the 

 double dark slide, &e. are not 

 pushed, but dropped in ; in this way 

 all trouble from jamming is avoided. 

 The dark slide is of tin, and is pressed 

 down by springs. 



Bagshaw's 'Elementary Photomicrography.' t— This little book 

 seems to correspond admirably with its title, and is written, as the 

 author says in the preface, for the purpose of encouraging amateurs to 

 commence the subject. It therefore aims at a clear exposition of prin- 

 ciples and arrangements ; and endeavours to show how many results can 

 be obtained with simple apparatus that almost any one might be sup- 

 posed to possess. There are ten chapters and an appendix, photomicro- 

 graphy with low powers being, naturally, more fully discussed than high 

 power work, where, however, some very useful hints are given. 



Kiohards, M. A. — Photomicroscopy of Metals as practised by Steel Companies. 

 [A useful practical paper.] 



Journ. App. Micr., V. (1902) pp 1920-6 (8 figs.). 



Fig. 26. 



* Zeitschr. f. wiss. Mikr., xviii. (1902) pp. 401-4 (1 fi 

 t Iliffe <te Sons. London, 1902, 68 pp. 





