MOUNTING OBJECTS IN THE DRY WAY. 313 



CHAPTEE VIII. 



METHOD OF MOUNTING OBJECTS IN THE DRY WAY. 



Many very delicate structures, when placed either in fluid or 

 in Canada balsam, lose several of their most striking charac- 

 ters ; these should be mounted dry. Amongst them may be 

 mentioned sections of teeth and bone, and of some kinds of 

 wood, hairs of animals, scales of butterflies, and other insects, 

 aU of which may be best examined in this condition. Various 

 methods have been practised from time to time ; one of the 

 oldest, perhaps, was that of enclosing the object between two 

 circular pieces of talc, which fitted into a hole cut out of wood 

 or ivory, and were kept there by a ring of brass wire, four or 

 more of these holes were made in one strip of ivory, and the 

 name given to it was a slider ; this plan is now only adopted 

 with the inferior microscopes, and has given place to others 

 more generally useful. 



First Method. — A thin plate-glass slide having been selected 

 and cleaned, the object is to be laid upon it, and over this is 

 placed a cover of very thin glass, a little larger each way than 

 the object ; the plan of securing the cover is as follows : — If a 

 very liquid cement were used, it would immediately run 

 between the glasses and obscure the object; therefore if gold^ 

 size be selected, it should be the oldest and toughest. Thick 

 sealing-wax varnish has less tendency to run in, but the best 

 cement of all will be found to be that described at page 276, 

 as being used for electrical purposes; this, when melted in 

 a ladle, can be laid on with a brush, and afterwards made 

 very smooth with a piece of iron wire heated in the spirit 

 lamp, and when cold can be trimmed ofi" in any way by a 

 knife; as soon as the angle between the cover and slide is 

 filled up, the cover may be more securely fastened down by 

 employing the gold-size or one of the liquid cements ; either 

 of these, besides adding to the strength of the first coat, may 

 be employed as the colouring agent, and so improve the 

 appearance of the mounting as well. 



