Journal of Applied Microscopy. 505 



exactly the same position. The polarizer can be swung aside when polarized 

 light is not desired. The prism is so arranged that it can be rotated, and is 

 provided with a circle graduated in degrees. The analyzing Nicol is also pro- 

 vided with a graduated circle, and is so mounted that it fits over and above any 

 eyepiece. The draw-tube of the microscope is furnished with a small projecting 

 pin which fits into a slot cut in the bottom of the tube mounting of the analy- 

 zer. This slot lies in the same vertical plane as the zero points of the analyzer, 

 the polarizer, and the stage. The zero points of polarizer and of analyzer are 

 arranged as usual, i. e., for the position of crossed Nicols. It follows, therefore, that 

 when the polarizer is at zero, and is swung in position below the stage, and the analy- 

 zer is also at zero and is in position with its slot on the pin, the Nicols are crossed 

 without further adjustment. It is therefore possible to quickly change eye-pieces, 

 drop the analyzer in place, and not be obliged to spend time in adjusting it as is 

 usually the case. The writer is not familiar with any other instrument of 

 corresponding price, in which the polarizing apparatus is so conveniently 

 arranged. 



Although the best results are to be obtained, as a general rule, by using high 

 objectives and low eye-pieces, it is quite evident that in micro-chemical work the 

 reverse is true ; the rule here being always a low objective and a higH eye-piece, 

 thus removing the objective as far as possible from corrosive vapors rising from 

 liquids on the stage. Since, then, an increased magnification is brought about 

 by changing eye-pieces, rather than objectives, the necessity of having the 

 analyzer mounted in some such way as described above becomes apparent. 



Each eye-piece is provided with cross hairs at right angles, and a projecting 

 stud fitting into a nick in the upper edge of the draw-tube for lining them. 



It will be seen from the above description that the instrument is in reality a 

 simplified petrographical microscope, but it should be borne in mind that it is 

 not intended as a substitute for such a stand, nor is it intended for crystallo- 

 graphic investigations. 



In the laboratory of the writer each instrument is provided with one-inch, 

 one-half-inch, and one-fourth-inch objectives; and two-inch, one-and-one-half- 

 inch, one-inch, and one-half-inch eye-pieces. This gives a range of magnifica- 

 tion lying between about 20 and 500 diameters, which is amply sufficient for all 

 ordinary analytical work. 



The draw-tube of the microscope is graduated as usual ; the mirrors, plane 

 and concave, are on a swinging bar. 



These instruments have proved so satisfactory that they can be recommended 

 to any one who is in search of a low-priced microscope for chemical work or 

 for food examination. E. M. Chamot. 



Chemical Laboratory, Cornell University. 



Dr. Ellet O. Sisson, formerly director of the Microscopical Laboratories in 

 the College of Physicians and Surgeons of Keokuk, Iowa, has been elected 

 director of the Histological Laboratory in the recently consolidated medical 

 schools of that city. 



