518 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



The substage-bar carries the usual centering fitting for condenser, 

 &c., and swings forwards or backwards concentric with the object on 

 the main stage, and the obliquity of the swing can be registered on a 

 graduated ring immediately behind the stage. The construction is 

 similar to that known as the Eoss-Zentmayer. An extra swinging 

 bar is attached behind, into which the mirror can be slid for use in 

 combination with the condenser, &c. 



We understand the swinging substage will be somewhat modified 

 by Messrs. Watson in future constructions. 



Eye Shade for Monoculars. — Mr. E. Pennock, of Philadelphia, 

 has devised for use with monocular Microscopes the eye shade shown 

 in Fig. 120. The microscopist is always supposed to keej) the eye 



Fir;. 120. 



Fig. 121. 



not in use open, but it is well known that there are many who are 

 unable to do so except at the sacrifice of the visibility of the details 

 of the object, especially when, as at soirees and public exhibitions, there 

 is a considerable glare of light upon the table on which the Micro- 

 scope stands. Seme of the devices hitherto 

 in use have been more elaborate than that 

 now proposed, which has the merit of the 

 utmost simplicity and prevents the possi- 

 bility of other objects being confused with 

 the microscopical image. It slips over the 

 cap of the eye-piece. 



Diagonal Rack-work and Spiral Pinion. 

 — The occasional application of diagonal 

 rack-work and spiral pinion to the me- 

 chanism of the Microscope, dates back from 

 at least the days of Andrew Pritchard. In 

 recent years it has also been adopted, par- 

 ticularly by Eoss and by Swift, the latter 

 using it throughout his construction of in- 

 struments. From the experience that we 

 have had of this arrangement, we find that 

 it produces a smoother motion than the 

 usual straight rack and pinion ; the spiral pinion gripping the rack 

 over a broader surface and holding it for a longer space during the 

 mf>tion. 



