ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



133 



plane face H (fig. 27) on one side, through whicli parallel rays making 

 an angle of 68° with the optic axis may be transmitted without con- 

 densation, as in Woodward's prism, A swinging shutter-diaphragm E, 

 of blackened brass, forming a shell-like quadrant exterior to the illu- 

 minator, is suspended on pivots G G (fig. 27) on either side of the 



Fig. 28. 



illuminator, so that it can be swung to shut off light from the plane 

 or lenticular edge. The rotation of the disk B allows either edge of 

 the glass disk I) to be presented to the source of illumination. A 

 slit-diaphragm cut through a very thin brass disk is placed on the 

 upper surface of B, and completes the device. 



No plan of mounting the semi-disk, or prism, or hemisphere, can, 

 we think, be considered advantageous in which they are not left 

 entirely free of the rectangular mechanical motions of the object- 

 stage. As regards the use of a slit-diaphragm in connection with the 

 swinging shutter, we possess a device, made seven years ago by ToUes, 

 in which the slit is cut through the swinging shutter, which we think 

 will be found the more convenient arrangement. 



Adams, J. M. — The Microscope among Infinities. 

 [Speculations on the limits of perception.] 



The Microscope, II. (1882) pp. 164-5. 

 „ „ How to turn over Small Objects. 



[" A simple and convenient way of turning over small objects, as corpuscles, 

 epithelium, diatoms, &c., in a liquid, is to half fill a live-box and revolve 

 the stage or hold the instrument so that it can be swayed out of level or 

 from one side to another. In this way all sides can be easily and readily 

 seen."] 



The Microscope, II. (1882) p. 165. 

 Blackbuest, W. — The Theory of Aperture in the Microscope : a popular exposi- 

 tion. North. Microscopist, II. (1882) pp. 325-34 (11 figs.). 

 Blackham, Gr. — Presidential Addresses at the Elmira Meeting of the American 

 Society of Microscopists. 

 [The Evolution of the Modern Microscope, &c. Cf. Vol. II. (1882) p. 698. 

 Appendix of leading facts in the lives of E. B. ToUes, E. Gundlach, 

 W. H. Bulloch, and the Bausch and Lomb Optical Co.] 



Proc. Amer. Sac. Micr., 5th Ann. Meeting, 1882, pp. 4-5, 5-8, 25-47. 



