ON MOUNTING. 153 



devices for selecting and transferring diatoms, &c., 

 to the cover were both cumbersome and uncertain 

 in their use and action, and that diatoms when 

 picked up by means of a hair, a bristle, or a brush, 

 of which the point was coated with gum, or some 

 other sticky substance to which they adhered (or 

 did not adhere), resulted in constant loss of rare and 

 valuable forms, in course of transference to the 

 cover, breakage, loss of time, and general uncleanli- 

 ness, he invented, for his own use, the " Diatom 

 Mounting Stage," of which the accompanying 

 diagram is an exact and full-size illustration. 



This stage is, of course, intended to replace the 

 ordinary mechanical stage of the microscope, and 

 that stage being temporarily removed, the diatom 

 stage is firmly fixed to the flat table of the main 

 stage by means of two screws passing there- 

 through and screwed into the diatom stage. The 

 stage must, of course, be so made that the central 

 circular orifice shall precisely coincide with that of 

 the stage of the microscope with which it is to 

 be used. Its description and the manner of its 

 employment are as follows : A A is a flat brass 

 plate with a central circular orifice for the passage 

 of reflected light from the mirror of the microscope. 

 B B are grooved side-pieces, in which slides, very 

 smoothly and evenly, the frame C. This frame is 

 retained in position at any point in its upward or 

 downward movement by two springs D D. It has 

 also two smaller springs E E, the use of which will 

 be described presently. F is a slightly raised bar 

 ending in a handle G. H is the raised upper rim 

 of the stage through which a screw passes, I. J J 

 are the raised sides of the upper portion of the 



