296 SUMMARY OF CUREENT RESEARCHES RELATING TO 



very accurate centering, and very close approximate focusing. Having 

 mafle these claims for it, I commend the apparatus to the attention of all 

 workers with the Microscope, whose time is generally too valuable to waste 

 on matters such as this." 



Wales's Cover-carrier for Immersion and Dry Lenses.* — Mr. W. 

 Wales, in exhibiting a non-adjustable l/o in. objective with a cover-carrier 

 or cap, said that the idea of affixing a cover-carrier to a lens occurred to him 

 because of the fact that opticians are frequently held responsible for errors 

 of the manipulator in the use of non-adjustable lenses — that a non-adjustable 

 lens corrected for a 10 in. tube would sometimes be used on an 8 in. tube, 

 and this failing to produce good results, the optician would get the credit 

 for making a poor lens. Hence he had fitted a cover-glass to a cap made to 

 screw on to the front cell, or fitting over the objective, and had adjusted 

 and corrected the lens for that particular cover- glass, so that the objective 

 could be plunged down into any fluid without injuring it, and would always 

 be correct for a 10 in. tube without adjustment. 



In using an oil-immersion lens with the cover-cap, a drop of oil is 

 placed on the inside of the cover-glass, and the lens can be used in urine, 

 blood, or other liquids. The oil can be allowed to remain there if the lens 

 is perfectly tight, saving time and trouble in repeated examinations of this 

 kind. The cap also serves as a protection to the lens. It can be easily re- 

 moved and cleansed at any time, and the cover-glass can be replaced if broken. 



Paper for Cleaning the Lenses of Objectives and Oculars.f — Prof. 

 S. H. Gage for the last two years has used the so-called Japanese filter 

 paper (the bibulous paper often used by dentists when filling teeth) for 

 cleaning the lenses of oculars and objectives, and especially for removing 

 the fluid used with immersion objectives. Whenever a piece is used once 

 it is thrown away. It has proved more satisfactory than cloth or chamois, 

 because dust and sand are not present, and from its bibulous character it is 

 very efficient in removing liquid or semi-liquid substances. At the author's 

 suggestion it was tried in the Bureau of Animal Industry at Washington, 

 and is now used there almost exclusively. 



Dallinger, W. H. — The value of the new Apochromatic Lenses. 

 [Extract from Presidential Address, supra, p. 185.] 



Nature, xxxv. (1887) pp. 467-9. 

 F ORGAN, W. — Notes on Microscope Objectives. 



Tr.nis. E.liuhur.ih Naturalists' Fidd Club, I. (1885-6) pp. 326-9. 

 Laurent, L. — Sur I'execution des objectifs pour instruments de precision. (On making 

 objectives for instruments of precision.) 



Comptes Rendns, CII. (1886) pp. 515-8 (2 figs.). 

 Nelson, E. M. — Object-glasses. 



[" For bacteriological work two lenses are absolutely necessary, and a Microscope 

 fitted with a cdudeiiKcr. I consider the condenser so important that I would 

 rather have an iudiiierent lens with a condenser than a first-rate lens without. 

 A cheap and excellent combination is Seibert Nos. 3 and 7, viz. a 1/2 N.A. 0'32 

 and water-immersion 1/16 N.A. 1"07. These two glasses cost a little under 5/., 

 and if you know how to test them you can get two first-rate lenses. A third 

 lens i.s very useful, as the interval between a 1/2 and 1/16 is rather wide. The 

 best lens to put in is a Keichert No la ; this is a 1/7 of N.A. 0'84. I tiiink its 

 price is about 21. The next series of three, costing about 9/., would be Zeiss 

 A. A., D.D., and G. These are a 2/3 of N.A. 0-31, a 1/6 N.A. 0-82, and a 1/9 

 N.A. 1 • 16. These also require selecting."] 



Ewil Mech., XLIV. (18R7) pp. 562-3. 

 ScHULZE, A. — On Abbe's Apochromatic Micro-objectives and compensating eye-pieces 

 made of the new optical glasses in the works of Dr. Carl Zeiss in Jena, with some 

 general remarks on object-glasses. 



Paper read to Glasgow Phil. Soc, 17th Nov., 1886, 13 pp. 



• Journ. New York Micr. Soc, ii. (1886) pp. 125-6. 

 t The Microscope, vi. (1886) p. 267. 



