35 G ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



greater improvement of dry lenses. Another notice, espe- 

 cially of the oil-immersion one-twelfth of Zeiss, by Adolf 

 Schultze, in a recent number of the English Mechanic, states 

 that the field is perfectly flat, and that the brilliancy and def- 

 inition leave nothing to be desired. This author states that 

 lie has failed to see, both with the one-eighth and one-twelfth 

 oil-immersion lenses, more than with the Powell and Lea- 

 land excellent new formula, or some other first-class water- 

 immersion lenses; yet, considering that no adjustments were 

 to be made to the Zeiss objectives, he could, upon the whole, 

 see everything better and easier with these. We have been 

 informed that the results obtained by Dr. Woodward, U.S.A., 

 in photographing by aid of these new objectives, are quite 

 equal to anything he has accomplished with any other first- 

 class modern objectives. The result of a comparison of the 

 one-eighth oil-immersion w T ith the new one-tenth and one- 

 sixth water- and glycerin -immersion objectives of C. A. 

 Spencer & Sons showed that the Zeiss objective, though 

 pressing very closely, was nevertheless somewhat inferior to 

 the Spencer objectives, especially by daylight, and when 

 using very high oculars ; still, the manifest advantages of 

 the oil-immersion were so great that the latter firm are now 

 perfecting a system on this plan, and microscopists are un- 

 der great obligations to Professor Abbe and Mr. Carl Zeiss 

 for this new departure, which promises so much. 



Immersion Condensers. 



In utilizing the increased angle of aperture obtained by 

 the new immersion objectives, an immersion illuminator is 

 required, and that devised by Professor Abbe is said to have 

 a balsam angle of 138. The reflex illuminator of Mr. Wen- 

 ham has also been used with great advantage, also Dr. Wood- 

 ward's arrangement of prisms, the under surface of the slide 

 being connected with these illuminators by means of glyce- 

 rin. Mr. Tolles long ago suggested the use of a hemispher- 

 ical lens thus cemented or attached to the under surface of 

 the slide ; and Mr. George Wale, of Paterson, N. J., simplifies 

 the whole matter by attaching a small prism, three eighths 

 by a quarter inch, without any mounting whatever, to the 

 under surface of the slide, by means of glycerin. 



