ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 761 



microscope -tube and an objective of long focus may be easily overcome. 

 A small stage of vulcanite or some other material, with an aperture of 

 about l|-in. diameter, is attached to the top of the substage fitting. By 

 this means an extra 2-in. of space between the objective and the object 

 is secured. 



Though the device is worth recalling it is far from new ; the last 

 recorded instance being that by Tathain in a paper read at the Quekett 

 in 1895.* 



Bacteriological Demonstration Table.f — M. Neisser gives a de- 

 scription of the Mikroskop-Karussel, by means of which microscopic 

 preparations of bacteria may be demonstrated to a seated class. Twelve 

 Microscopes are placed at equal distances from one another, upon an iron 

 table which can revolve round a central axis. Each Microscope is placed 

 at a suitable distance from the edge, and is provided with a separate source 

 of light. A wooden rim, which does not move with the rest of the table, is 

 used as a rest for the elbows of the students. Beside the teacher's seat 

 is a lever by means of which the table may be fixed or released, and a bell, 

 to give signal when the table is about to be moved. The demonstrator 

 places a specimen in focus under the Microscope facing him, releases 

 the table and turns it so that the specimen is suitably placed for 

 examination by his right-hand neighbour, mounts another specimen and 

 moves it on. This continues until each Microscope-stage carries an 

 object, and the whole class is provided. The general idea is simple, but 

 the construction of a satisfactory table requires considerable attention to 

 detail. The chief requirement is stability, but it is also essential that 

 there shall be no jarring in the movement or in the operation of the 

 controlling mechanism. 



(3) Illuminating and other Apparatus. 



Measuring Inclination of Abbe's Drawing Apparatus.! — W. 

 Georgi points out that, if the mirror of the large Abbe drawing 

 apparatus be at its normal inclination of 45° to the vertical, only one- 

 half of the microscopic field can be drawn. In order to bring in the 

 whole field, it is necessary to change the inclination of the mirror. If 

 the drawing board be not similarly adjusted, a distorted picture Avill be 

 obtained. This board should make with the horizontal an angle twice 

 as great as that which the mirror makes with its normal inclination. 

 The author's device to simplify this adjustment is to affix scales to both 

 drawing board and mirror. 



Improvements in the Leitz Mirror Condenser.§ — W. von Igna- 

 towsky points out that the hollow space in the Leitz condenser (fig. 107 > 

 makes it necessary to construct the apparatus out of two pieces of glass 

 cemented together. In the process of manufacture, however, it is not 

 possible to obtain perfect precision in the application of the plane sur- 

 faces and the small irregularities therefore detract from perfect efficiency. 



* Joum. Quekett Micr. Club, v. (1894-7) p. 206. 

 t Urnschau., siv. (1910) pp. 112-13. 

 j Zeitschr. wiss. Mikrosk., xxvii. (1910) pp. 94-114. 

 § Op. cit., xxvi. (1910) pp. 387-90 (1 pi. and 3 figs.) 



Dec. 21st, 1910 3 E 



