1889.] MICROSCOPICAL JOITKNAL. 53 



Fig. 2 represents an arrangement for heating microscopic objects 

 during observation, according to Pfeiffer's design. It will be seen that 

 the microscope stage is within the apparatus, the body-tube projecting 

 from the top. By this construction the temperature of the object is 

 known to a certainty, as the object, stand and surrounding air are all 

 at the same temperature, and can be maintained so for any length oi 

 time. A temperature of 40" C. may be maintained without injury to 

 the stand or objective. This apparatus is made of two sizes, costing, 

 respectively, 60 and 70 marks. 



A new objective carrier and changing device is illustrated in fig. 3. 

 Each objective can be accurately centered by means of an ordinaiy 

 watch-key. As the objective slides in, on an inclined plane, the change 

 can be made without danger of injuring the mounting of the specimen. 

 The construction can readily be understood from the figures. 



American and European Microscopes. 



By H. J. DETMERS, 



COLUMBUS, OHIO. 



[The following, extracted from the Proceedings of the American Society of Microscopists, 1888, 

 represent-; the substance of Dr. Detmers' remarks, and is republished here as a substitute for the report 

 given on pages 187 and 188 of last year's Journal, Dr. Zeiss having stated that that report was quite 

 untrue, and Dr. Detmers having confirmed that statement. — Editor.] 



At the meeting in Pittsburgh (1SS7) I had occasion to make some re- 

 marks concerning an examination of a new Zeiss apochromatic y^-inch 

 homogeneous immersion objective, N. A. 1.40, and its workings with 

 its compensating and projecting eye-pieces. I compared its performance 

 by central and oblique light on test objects and on bacteria, etc., with 

 that of some of our best American objectives, but particularly with a ^j- 

 inch homogeneous immersion objective of Tolles, N. A. 1.30. The 

 conclusions arrived at I expressed in the following words: "I am 

 convinced that the apochromatic objective examined in no way sur- 

 passes the best work (objectives) of our best American makers." This 

 sentence evoked considerable discussion. I therefore offered to back 

 my statement with facts ; to photograph Amphipleura pellucida with 

 oblique, and bacteria with central light, with American objectives and 

 American accessories, and challenged my opponents to produce as good 

 or better work with European apochromatic objectives, if they could. 

 I made this offer because photo-micrography, it must be admitted, con- 

 stitutes the crucial test for perfect achromatism, and hence for the very 

 quality in which the new apochromatic objectives are claimed to be 

 superior to all others. I have done what I promised, have made the 

 photo-micrographs of Amphipleura pelhtcida and of several bacteria 

 — amplification 1 120 and 692 diameters, respectively — and hand them to 

 the members of the Society for inspection. 



Since the Pittsburgh meeting, I have made a trip to Germany, from 

 whence I returned only last week. In Germany I visited three of the 

 principal optical establishments of that country, namely, those of Ernst 

 Leitz, in Wetzler, of Seibert & Seibert, in Wetzler, and of Dr. Carl 

 Zeiss, in Jena. I stopped one day in Wetzler and one day in Jena. 

 The proprietors of all three establishments received me with great kind- 



