180 



THE MICROSCOPE AND ITS REVELATIONS. 



required, it can be made in the manner suggested by Prof. H. L. Smith 

 (U.S.) specially for the mounting of Diatoms. A sheet of thin writing- 

 paper dipped into thick shell-lac varnish is hung up to dry; and rings 

 are then cut out from it by punches of two different sizes. One of these 

 rings being laid on a glass slide, and the cover, with the object dried 

 upon it, laid on the ring, it is to be held in its place by the forceps or 

 spring-clip, and the slide gently warmed so as cfause a slight adhesion of 

 the cover to the ring, and of the ring to the slide; and this adhesion may 

 then be rendered complete, by laying another glass slide on the cover, and 

 pressing the two slides together, with the aid of a continued gentle heat. 

 Still deeper cells may be made with rings punched out of tin-foil of 

 various thicknesses; and cemented with shell-lac varnish on either side. 

 And if yet deeper cells are needed, they may be made of turned rings of 

 vulcanite or ebonite, cemented in the same manner. It is always safer 

 to protect such dry mounts by attaching paper covers to the slides; as the 

 tendency of the rings to start at any 'jar,' when the shell-lac has re- 

 acquired its resinous hardness, is thereby greatly diminished. Small 

 objects, such as Diatoms and Polycystina, which are to be viewed by 

 Lieberkuhn illumination ( 115), should be mounted on disks punched 

 out of thin black card-board, whose diameter scarcely exceeds the field 

 of the Objective under which they are to be shown; and the protecting 

 cell should be large enough to allow an ample opening for the light-rays 

 to pass up from the mirror to the speculum, between the inner edge of its 

 ring and the outer margin of the disk. 



170. Cement-Cells. Cells for mounting thin objects in any watery 

 medium, may be readily made with Asphalte or Black Japan varnish, by 

 the use of Mr. Shadbolt's ' Turn-table' ( 17G) or one of its modifications. 



The glass slide being placed under 

 its springs, in such a manner that its 

 two edges shall be equidistant from 

 ^ the centre (a guide to which posi- 

 tion is afforded by the circles traced 

 on the brass), and its four corners 

 equally projecting beyond the cir- 

 cular margin of the plate, a camel s 

 hair pencil dipped in the varnish 

 B is held in the right hand, so that 

 its point comes into contact with 

 the glass over whichever of the 

 circles may be selected as the guide 

 to the size of the ring. The turn- 

 table being , made to rotate by the 

 c application of the left fore-finger 

 to the milled-head beneath, a ring 

 of varnish of a suitable breadth is 

 made upon the glass; and if this be 

 set aside in a horizontal position, 

 it will be found, when hard, to 

 present a very level surface. If a 

 greater thickness be desired than 



' a single application will conveni- 



Tube-ceiis, Bound and Quadrangular. ent i y 6 ma ke, a second layer may be 



afterwards laid on. It will be found convenient to make a considerable 

 number of such cells at once, and to keep a stock of them ready prepared 



Era. 



