MOUNTINfi OPAQUE OBJECTS FOR LIEBERKUHN. 223 



thickened with starch. The complete protection thus given to 

 the object, is the great recommendation of this method ; since, 

 when objects are simply fastened on black paper gummed on a 

 slip of glass, their protection from its surface renders them con- 

 stantly liable to accidents ; as many know, to their cost, who 

 have used that mode of mounting. But this is by no means 

 its only convenience. It is far cheaper than mounting objects 

 in glass cells, which is the only other mode of affording them 

 protection, save the use of pill-boxes in the manner to be pre- 

 sently described. It allows the slides, not only to range in 

 the ordinary cabinets, but also to be laid one against another, 

 and to be packed closely in cases or secured by elastic bands ; 

 and this last plan is extremely convenient, not merely for the 

 saving of space, but also for preserving the objects from dust. 

 Should any more special protection be required, a thin glass 

 cover may be laid over the top of the cell, and secured there by 

 gummed paper ; but this will, of course, occasion a slight pro- 

 jection, which will expose the glass cover to the risk of fracture 

 when the slide is pressed against others ; and the Author's ex- 

 perience leads him to conclude, that the mode of packing just 

 described affords a security from dust, that is scarcely less effec- 

 tual than a thin glass cover. Further, the card on the under sur- 

 face affords a great convenience for writing on the slide the name 

 and other particulars of the object. If the object be so large as 

 to project above the surface, even when the thickest slides are 

 used which it is convenient to employ, an additional protection 

 may be afforded, by gluing a couple of strips of wood of adequate 

 thickness along the edges of the slide ;' or by gumming a second 

 slide to the face of the first, taking care that its aperture be large 

 enough to prevent obstruction to oblique light. Very delicate, 

 flat objects, on the other hand, even when to be viewed by inci- 

 dent light, should be mounted on glass and protected by a cover, 

 in the same manner as transparent objects ; a dark background 

 being furnished to them, either by the "dark well" (§ 65) or by 

 the closed diaphragm (§ 55). 



124. Objects which are to be viewed by the Lieberkiihn should 

 be mounted either on flat disks of card, or cork, or, if protection 

 be desired, in cups of proper depth, resembling very shallow pill- 

 boxes, which may be made with or without covers,^ of any size 



' A very convenient kind of slide, for mounting large opaque objects, is made by 

 Messrs. Carpenter and Westley, 24 Regent Street, by ploughing out a groove in a strip 



of wood, so that its section presents this form I i. The object may be mounted upon 



the bottom of the groove ; or upon a disk of card fitted into an aperture in the slide, and 

 so held there by a brass ring, that it may be taken out and held between the stage-for- 

 ceps, so as to be viewed with the Lieberkflhn. These slides are commonly made five 

 inches long, and are fitted for the reception of four objects ; for the sake of uniformity, 

 however, as well as for preventing them from overbalancing on the stage, it might be 

 convenient that they should be made three inches long, and that each should only 

 receive one or (at most) two objects. 



* Round boxes with glass covers are now coming into very extensive use for the pre- 

 servation of Natural History specimens of various kinds, in such a manner that the cSn- 



