1890.] MICROSCOPICAL JOURNAL. 67 



The cement ring is finished at one application, enough being applied 

 to produce a well rounded ring. In a few hours the slide is ready for 

 the cabinet. 



Bell's cement has been found at times to work unsatisfactorily, not 

 flowing freely from the brusli, and forming large bubbles in the ring, 

 particularly in a warm room. The addition of a very little chloroform 

 to the cement, and thorough mixing, produces a material that works 

 smooth!}' and dries with a satisfactory finish. 



The Filar Micrometer. — The following description is from the 

 Proceedings of the American Society of Microscopists for 18S9: 



An internal frame is provided with a longitudinal and transverse 

 cross-hair, which is adjustable within a limited range for position by a 

 milled head at one end. The micrometer screw, which is cut accord- 

 ing to desire, either to ^ millimeter or g^ inch, is adjustable by grad- 

 uated disk and carries the cross-hair across the field. The graduation 

 is in 100 parts on a silvered ring, and the reading is made from a sta- 

 tionary index. The graduated disk may be revolved on its axis. A 

 comb is in the field, corresponding exactly with the pitch of the screw, 

 thus enabling the determination of the number of revolutions. A 

 Ramsden eye-piece is used, which is stationary in the optical axis and 

 adjustable for focus. The apparatus is extremely delicate, and adjust- 

 able to any tube. 



Through some error of the editor or committee the article above- 

 quoted is entitled " Nezv accessories of the Bausch and Lomb Optical 

 Company," but Messrs. Bausch and Lomb do not claim anything new 

 therein. They have made their micrometer to accord with sugges- 

 tions of Dr. M. D. Ewell of what he considered correct principles. 

 The real credit for originating the secondary slide, adjustment seems 

 to belong to Mr. Walter H. Bullock, who claims that he has been 

 making them for five or six years and who announced the same in this 

 periodical in 1S85, page 139, as well as in the Journal of the Royal 

 Microscopical Society for February, 1886, page 132. 



o 



Death of J. L. De La Cour. — De La Cour, who died Dec. 26, 

 18S9, was one of the organizers of the Camden Microscopical Society, 

 and for many years took an active interest in microscopy. He was 

 well known all over the country, and never tired of organizing societies 

 when applied to, as he frequently was. 



o 



The Jena Optical Works. — Dr. E. Abbe, who until lately acted 

 as a plenipotentiary of the firm of Carl Zeiss in Jena, entered the firm 

 as a co-partner of Dr. Roderick Zeiss on the 29th of November. He has 

 taken upon himself the sole management of the firm's business. Dr. 

 Roderick Zeiss has retired from active participation in the business, 

 though his interest in it is still considerable. 



At the same time Dr. Otto Schott and Dr. vSiegfried Czapski have 

 been authorized to represent the firm. 



Dr. Schott and Dr. Czapski are both well-known for their special 

 acquirements in theoretical and practical optics, the former having 

 hitherto had the direction of the Jena Optical Glass Works, wdiilst the 

 latter has been Prof. Abbe's assistant during several years, and a fre- 

 quent contributor to German scientific journals. 



