313 



The Microscope. 



the ground glass of the camera when the objective of lowest power 

 is used. Then, when higher powers are used, the prism -tube and 

 image are kept at the same level by simply drawing out the draw- 

 tube of the microscope for a short distance. 



The projecting cone 

 seen in Fig. 2, attached 

 to the front-board of 

 the camera, is made of 

 tin, may he of any 

 reasonable length, and 

 will cost but a trifle. It 

 is connected to the 

 , prism-tube by a cloth 

 :dcap, which permits the 

 slight motion needed in 

 focusing with both coarse and fine adjustments. 



Since writing the above, I have been told by Mr. Zentmayer, 

 Jr., that after receiving my order (about April 15th), he received 

 designs from, and made a somewhat similar appliance, for Mr. J. C. 

 Boyee, of Pittsburgh, Pa. 



If I am not mistaken, it was used at the exhibition of the Pitts- 

 burgh Microscopical Society, May 25th, with a binocular stand, to 

 allow two persons to observe the same object at the same time; the 

 visitor looking through the appliance at one side, while the exhibitor, 

 using the other tube of the microscope, managed the focusing, 

 described the object, etc. 

 Philadelphia, Pa. 



Fig. 2. 



EDITORIAL. 



SUB -STAGE CONDENSERS. 



VX y' ITH the low-angled objectives of a few years ago, a sub-stage 

 ' * condenser was an indispensible accessory for work with 

 high powers. As the aperture of objectives increased, the demand 

 for sub-stage condensers diminished, and they were buc rarely used. 

 The stimulus that has been given to working with high-power by 

 bacteriological discoveries, and the necessity in the study of bacteri- 

 ology of adjunctive high illumination, has again made the subject 

 of sub-stage condensers one of great importance. Although the 

 objective or eye-piece adjusted to the sub-stage, the Wenham button, 

 and others, have served a good purpose, they are inadequate to the 



