944 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the velvet and the polished glass, and below between the ivory knobs 

 and the glass surface. The friction can be somewhat increased by 

 tightening the milled-head screws. An adjustable spring-clip keeps 

 the object in position. 



ToUes's Mechanical Stage. — Mr. ToUes has now further improved 

 the stage described pp. 116-118 (Figs. 9 and 10). The improve- 

 ments are comprised under four heads: — (1) The application of 

 a rim or flange to the main stage-ring or support above the general 

 plane of the stage. (2) The countersinking of the rotating stage- 

 plate into the stage-ring. (3) The use of one plate only for the 

 rectangular motions of the stage. (4) The union upon one axis of the 

 milled heads controlling the rectangular motions. 



(1) The upper surface of the main stage-ring H was formerly 

 flat, and formed a bedding for the rotating plate C, the milled 

 edge of the latter projecting slightly, for convenience of turning 

 by the hand : a rim or flange is now applied to the ring H, outside 

 the plate C, and is carried up to the shoulder by a gradually 



Fig. 221. 



increasing vertical thickness of metal, by which the rigidity of 

 the stage is considerably added to. The shoulder forms a sub- 

 stantial attachment to the vertical disk which is fixed to the limb of 

 the Microscope, and in which the substage and mirror slide laterally, 

 concentrically with the object upon the stage (see Mr. Tolles' special 

 form of traversing substage figured vol. iii. (1880) p. 521). Mr. 

 Tolles' plan of making the rectangular and diagonal movements act 

 completely tvUMn the circumference of the stage, has enabled him to 

 strengthen the rim of the stage-ring above the general plane instead 

 of below it ; the inner jmrt of this ring-support is flanged so that the 

 rotating stage plate is countersunk flush with the thinnest part of 



