450 PREPARATION, MOUNTING, AND COLLECTION OF OBJECTS 



This piece being rejected, the four strips are then to be cemented 

 upon the glass slide in their original position, so that the diamond-cuts 

 shall fit together with the most exact precision; and the upper 

 surface is then to be ground flat with emery upon a pewter plate 

 and left rough. The perfect construction of large deep cells of this 

 kind, as shown in fig. 378, A, B, however, requires a nicety of work- 

 manship which few amateurs possess, and the expenditure of more 

 time than microscopists generally have to spare ; and as it is conse- 

 quently preferable to obtain them ready-made, directions for making 

 them need not be here given. 



Wooden Slides for Opaque Objects. Such 'dry' objects as/bra- 

 minifera, the capsules of mosses, parts of insects, and the like, may 

 be conveniently mounted in a very simple form of wooden slide (first 

 devised by the Author and now come into general use), which also 

 serves as a protective ' cell.' Let a number of slips of mahogany or 

 cedar be provided, each of the 3-inch by 1-inch size, and of any 

 thickness that may be found convenient, with a corresponding 

 number of slips of card of the same dimensions, and of pieces of 

 dead-\)\Sick paper rather, larger than the aperture of the slide. A 

 piece cf this paper being gummed to the middle of the card, and 

 some stiff gum having been previously spread over one side of the 

 wooden slide (care being taken that there is no superfluity of it 

 immediately around the aperture), fchis is to be laid down upon the 

 card, and subjected to pressure. 1 An extremely neat ' cell' will thus 

 be formed for the reception of the object, as we see in fig. 37i>. the 



depth of which will be deter- 



^g^^~ \ mined by the thickness of the 

 ^MJHItl \ slide, and the diameter by the 

 ^tijfJr \ si z e of the perforation ; and it 

 =3 will be found convenient to 



FIG. 379. Slip made of wood. provide slides of various thick- 



nesses, with apertures of diffe 



rent sizes. The cell should always be deep enough for its wall to 

 rise above the object ; but, on the other hand, it should not be too 

 deep for its walls to interfere with the oblique incidence of the light 

 upon any object that may be near its periphery. The object, if fiat 

 or small, may be attached by gum-mucilage ; if, however, it be large, 

 and the part of it to be attached have an irregular surface, it is 

 desirable to form a ' bed ' to this by gum thickened with starch. If, 

 on the other hand, it should be desired to mount the object edgeways 

 (as when the mouth of nforaminifer is to be brought into view), the 

 side of the object may be attached with a little giun to the wall of 

 the cell. The complete protection thus given to the object is the 

 great recommendation of this method. But this is by no means 

 its only convenience. It allows the slides not only to range in 

 the ordinary cabinets, but also to be laid one against or over 

 another, and to be packed closely in cases, or secured by elastic 

 1 It will be found a very convenient plan to prepare a large number of such slides 



at once, and this may be done in a marvellously short time if the slips of card have 

 been previously cut to the exact size in a bookbinder's press. The slides, when put 

 together, should be placed in pairs, back to back, and every pair should have each 



