1894.] MICROSCOPICAL JOURNAL. 353 



forated ring-shaped sheet of copper, which can be heated as de- 

 sired by means of two Biinsen burners. It is also affixed to a 

 special insulating support to prevent any heat being conducted 

 to the body of the microscope. As the object cannot, therefore, 

 be turned or moved in its plane, the entire microscope (with 

 which the polarizer is firmly connected) can be made to revolve 

 in a horizontal semi-circle, and it can also be moved horizon- 

 tally by means of two guides. The motions provide for the 

 measurement of inclinations due to extinction. The instru- 

 ment does not exactly measure temperatures, but some therrno- 

 metric substance. This microscope is in the opinion of the 

 Zeitschrift fur Instrumentenkunde, not suitable for making obser- 

 vations in convergent polarized light. — The Optician. 



Professor Gage's marking apparatus. — Attention is called 

 espicall}^ to the article on pages 334-5. The figure represents a 

 stage micrometer with a delicate ring of cement enclosing the 

 band of lines. This has the advantage of making the observer 

 certain that the lines are somewhere within the circle, and fur- 

 thermore, by focusing on the edge of the circle first, there is less 

 danger of breaking the micrometer as one knows he is about at 

 the point where the lines should appear. 



MICROSCOPICAL MANIPULATION. 



Freeborn's Method of Collecting Material — At a meet- 

 ing of the New York Pathological Society, held September 23, 

 1891, Dr. G. C. Freeborn made a report on a Method of Rap- 

 idly Collecting Deposits for Microscopic Examination, in which 

 he called attention to Litten's report, and himself demonstrated 

 a home-made machine capable of about nine hundred and 

 fifty revolutions per minute. This had answered the purposes 

 for which it was devised admirably. He concluded that "in or- 

 dinary urinary analysis not only would this new method enable 

 the microscopical examination to be made about twenty-four 

 hours sooner than formerly, but it would effectually prevent 

 decomposition of casts, which was liable to occur w^hen the 

 urine had to stand for many hours in order that the deposit 

 might settle." 



A Transparent Cement. — For cementing purposes, opti- 

 cians get the oldest Canada balsam they can obtain, and drive 



