520 SUMMARY OF CURRENT RESEARCHES RELATING TO 



applied to tlieir most recent ^^ (exhibited at the Society on November 

 10th last). 



The convenience of the adjustment has been lately brought out 

 remarkably in testing with the yV various media for immersion. For 

 instance, with the solution of sulpho-carbolate of zinc in glycerine, 

 having refractive index 1-.525 (nearly), the adjustment permitted the 

 lenses to be slightly approximated, and the result was a more perfect 

 correction than by using oil of cedar-wood. The correction-collar 

 was also employed advantageously (with the same lens) on various 

 specimens of Podura, some of which, not being in close proximity to 

 the cover-glass, could not have been viewed so well had the lenses been 

 mounted in a fixed setting. These facts w-ere plainly developed by 

 immediate comparisons with several oil-immersions in fixed mounts — 

 by Zeiss, Seibert and Krafift, Gundlach, and Powell and Lealand, which 

 failed to give correct images on all the scales that were not in very 

 close adherence to the cover-glass. 



Mr. A. H. Bragdon, of Bangor, Maine, U.S.A., also writes to us on 

 this subject, recommending Mr. Tolles's a2:)plication of the correction- 

 adjustment on the ground that the same objective that is corrected at 

 " closed " point for homogeneous immersion may be used for prelimi- 

 nary observations with water-immersion, the screw-collar enabling 

 the observer to adjust the lens for that mediimi. He states that, " to 

 the worker this is a great desideratum, and saves a multiplicity of 

 objectives. No one can appreciate this more than a physician who 

 constantly desires to examine with a high power many temporarily 

 mounted objects." 



Mr. Bragdon also mentions that he has received from Mr. Tolles a 

 solution of chloride of cadmium in glycerine of exactly 1 ' 525 index. 

 Since the receipt of his letter we have examined a specimen of the 

 fluid (sent by Mr. Tolles), and have found it work well with homo- 

 geneous-immersions provided with correction-adjustment, notably a 

 ^^ made by him, and Powell and Lealand's -^^ above mentioned. 



Seller's Large Stage. — Dr. Seiler, of Philadelphia, has devised a 

 large stage, arranged with mechanical movements, so that it can be 

 made to traverse a distance of about four inches each way. It is 

 claimed to be particularly valuable for examining large specimens, 

 such as sections of tumours, the vocal organs, or anything requiring 

 a large stage movement to bring the whole of the structure suc- 

 cessively into view. 



Sliding Stage Diaphragms. — Dr. J. Anthony writes as follows : — 

 "In going through a series of experiments during the last few 

 months, on the comparative advantages of diaphragms above and below 

 the condenser of the Microscope, I arrived at such satisfactory results 

 that it may be worth while to place them on record ; not as a finality, 

 for nothing is likely to be final with the Microscope for many a long 

 day, but that others may take up the matter where I leave it, and that 

 I may have the satisfaction of feeling that I have thought out a most 

 efficient and economic appliance so far as it goes. 



