802 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



Fig. 99. 



existed with direct-acting screw fine-adjustments, viz. that of providing- 

 a slow movement by means of coarse strong threads ; in all other direct- 

 acting screw fine adjustments, if they are slow enough to work wide- 

 angled oil-immersion objectives, the movement is obtained by means of 

 a micrometer-screw with a very fine thread, which is too weak to stand 

 the usual wear and tear. The milled head of the fine-adjustment is 

 placed below the limb. In this new position it is found to be quite con- 

 venient for ordinary work, while it is steadier when a cord is attached 

 for photomicrography. 



The stage is plain i^otary, having Mayall's mechanical movement 



attached ; it can be clamped 

 by the screw in front. The 

 substage has centering 

 movements, rack-and-pinion 

 coarse - adjustment, and 

 differential - screw fine-ad- 

 justment, admitting of 

 wide - angled condensers 

 being easily focused. The 

 usual plane and concave 

 mirrors on a double-jointed 

 arm are carried on an ad- 

 justable hinged tail-piece. 



Edinburgh Student's 

 Microscope. — This Micro- 

 scope (figs. 99 and 100) has 

 been made by Messrs. W. 

 Watson and Sons, on lines 

 suggested by Dr. Edington, 

 Lecturer on Bacteriology 

 at Edinburgh University. 

 Fig. 99 shows the instru- 

 ment in its simplest form, 

 with sliding body for 

 coarse-adjustment, Conti- 

 nental horse-shoe foot, and 

 body - tube of the Conti- 

 nental size, fitted with 

 draw-tube, which, when ex- 

 tended, gives the full 

 English length of 10 in. 

 The fine-adjustment — a part 

 often neglected in instru- 

 ments of Continental make 

 — is worked by the rota- 

 i tion of a milled head acting 

 on a lever moving the 

 -2-;;^=^ entire body. A tenth of a 

 turn of the milled head 



only moves the body 1/3000 in., so that a precise adjustment 



can be made. 



Another point is the hanging of the nnder-stage, fitted on a pivot 



so that it can be lifted aside with a condenser in it, and direct light 



