586 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



ri"ht 



position 

 clamping-ring slides 



beiug 



Fig. 117 



\ 



object-table a glass plate can be set, or a small drawing-board when the 

 apparatus is to be used for drawing to a reduced scale. With trans- 

 parent objects illumination is effected by a mirror S, or by a piece of 

 wbite paper. Tbe collar B 2 bears on its under side a bollow cylinder, 

 in wbicb works a rod carrying at its distal end tbe Microscope witb 

 reversing eye-piece. Tbe Microscope fits loosely into ring-sbaped 

 holders H 1? H 2 , H 3 , and may be replaced by spectacle glasses of various 

 strengths or by ordinary loups. Tbe drawing-prism (camera lucida) is 

 fastened on to tbe ocular tube of the Microscope in the usual way, the 



indicated by a pin, over which the slit of the 

 The Microscope is so set in the holder H that 

 the rotation-pin of the draw- 

 ing-prism is parallel to the 

 front edge of the drawing- 

 board. This drawing-board Z 

 is placed on a perforated desk- 

 shaped frame, which slopes at 

 an angle of 25° to the horizon, 

 and which, sliding in a groove 

 of the ground-plate, can be 

 pushed backwards and for- 

 wards perpendicularly to the 

 front edge of the object-table, 

 and can be clamped in any de- 

 sired position. In order to 

 attain a drawing of uniform 

 magnification, it is necessary 

 that the distance between the 

 pupil of the drawing-prism (a 

 small circular opening of the 

 prism-holder) and the draw- 

 ing-plan should be constant. 

 There are two scales T x T 2 on 

 opposite sides of the object- 

 table, and two similar scales 

 (fig. 117) on the drawing- 

 frame, and two on the base-plate. When the adjustments are made, a 

 line joining the two zeros on the object-table will be parallel to the zero 

 line on the drawing-frame. When, therefore, the arm A of the Micro- 

 scope is moved in and out of its sheath B 3 , the whole of the object can 

 be searched and delineated on the drawing-board. 



Acetylene Gas for Bacteriological Laboratories. * — C. H. Higgins 

 advocates the use of acetylene gas for isolated bacteriological labora- 

 tories. For general purposes it is preferable to ordinary coal gas, and 

 makes a most excellent artificial light for microscopical work, its spec- 

 trum being very nearly identical with that of the sun, lacking only th e 

 ultra-violet rays. The form of generator advised is one in which, by a 

 mechanical arrangement, the carbide is dropped into a large body of 



Centralbl. Bakt., 1" Abt., xxix. (1901) pp. 794-7. 



