318 MANIPULATION. 



and then the objects laid on it ; if it be necessary to keep 

 them in place, the smallest possible quantity of gum may be 

 applied to one corner ; the top plate is now to be laid on the 

 specimens, one of the edges is then to be heated in the flame 

 of a spirit lamp, and the groove filled with sealing-wax, as 

 shown at a; when one edge is done, the others are to be 

 heated in the same manner, until the entire groove is filled 

 with the wax, which thus acts two purposes, one to keep the 

 slides together, and the other to prevent the access of air. 

 The excess of wax may be cleaned off from the edges by 

 rubbing them upon sand-paper laid on a flat board, until they 

 are smooth ; if bright edges be required, they may be passed 

 quickly through the flame of the spirit lamp. It must, of 

 course, be borne in mind, that all objects mounted in this way 

 should be made perfectly dry before they are sealed up." The 

 author, some years ago, was presented with a collection of 

 sections of wood by Mr. Darker, which have not only kept in 

 their places, but are as perfect and as free from confervte as 

 when they were first received. They are all labelled after a 

 very excellent plan, viz., by having the generic and specific 

 name on one side of the label, and the popvilar on the other. 



CHAPTER IX. 



MOUNTING OPAQUE OBJECTS. 



Opaque objects may be mounted in various ways: — on discs, 

 on cylinders, on glass slides, or in cells. 



On Discs. — The discs consist of circular pieces of some soft 

 material, through which a pin is passed, they may vary in 

 diameter from a quarter to one inch : one kind may be con- 

 veniently made by glueing together two pieces of card-board, 

 with a piece of rather thick chamois leather between them, 

 and then cutting out with a punch discs of any required size. 

 Through the chamois leather a long but strong pin is to be 



