ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



505 



Holmes' Microscope with Swinging Radial Mirror. * — This 

 Microscope (fig. 92) was made by Mr. S. Holmes in 1872, and 

 is an anticipation of the principle subsequently adopted in the 

 ToUes-Blackham and similar Microscopes. The stage is attached to 

 a disc mounted on a slide which is raised or lowered by rack and 



Fig. 92. 



pinion (forming the only adjustment for focus). At the periphery 

 of this disc is a ring which is free to rotate between guides and to 

 which is attached the mirror. The latter can thus be rotated com- 

 pletely round a line drawn through the centre of the stage, thus giving 

 radial illumination above and below the stage. 



* The srfcand is Holmes' Isophotal Binocular, 

 diagonal rackwork to the stage-movement. 

 Ser. 2.— Vol. VI. 



There is a spiral pinion and 

 2 L 



