INVERTEBEATA, CRYPTOGAMIA, MICEOSCOPY, ETC. 



767 



A speciality of the stage is that the object is fixed to its under side, so 

 that no change of focussing is required with preparations mounted on 

 slides of varying thickness. The coarse adjustment is made by sliding 

 the tube carrying the objective through the outer one, and there is in 

 addition a special fine adjustment moved by a screw close to the 

 objective. 



By means of the handle and the fork at the end of the rod which 

 carries the stage, the instrument can be rested on the table without 

 any danger of injuring the slide. 



Fig. 2. Fig. 3. 



If in a preparation any point difficult to find is required to be 

 shown, the Microscope can be fixed in the base which carries a mirror 

 (shown in Fig. 3), and the preparation examined in the ordinary way. 



This instrument will be shown at the next meeting of the Society. 



Novel Method' for Focussing.* — The Societe de Biologie of Paris 

 devote a page of their ' Comptes Eendus,' just issued, to a descrip- 

 tion by M. d'Arsonval of an arrangement which he has devised for 

 focussing, " without touching either the object or the Microscope." 

 The inventor states that he discovered the method several years ago, 

 but neglected to communicate it, though at the same time he wishes it 

 to be understood that he makes no claim for priority. 



The idea was suggested to him by the observation that if an object 

 is viewed through a parallel plate of glass, it will appear the nearer 



* ' CR. Soc. Biol.,' xsix. (1877, pub. 1879) pp. 124-5. 



3 E 2 



