184 



THE MICROSCOPE AJSID ITS REVELATIONS. 



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 bands; which 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 either by a rim of gum or by a perforated paper cover 

 attached to the slide; and if it should be desired to pack these covered 

 slides together, it is only necessary to interpose guards of card somewhat 

 thicker than the glass covers. 



176. Turn-table. This simple instrument (Fig. 125), devised by Mr. 



Fio.125. 



FIG. 124. 



Wooden Slide for Opaque Objects. 



Shadbolt's Turn-table for making Cement-Cells. 



Shadbolt, is almost indispensable to the Microscop^st who desires to pre- 

 serve preparations that are mounted in any ' medium ' beneath circular 

 covers; since it not only serves for the making of those ( Cement-cells * 

 ( 170) in which thin transparent objects can be best mounted in any 

 kind of ' medium' but also enables him to apply his varnish for the secur- 

 ing of circular cover-glasses not only with greater neatness and quickness, 

 but also with greater certainty than he can by the hand alone. As the 

 method of using it for the latter purpose is essentially the same as that 



already described under the former 

 jria>i26 head, it need not be here repeated; 



the only special precaution to be ob- 

 served, being that the cover-glass, 

 not the slide, should be 'centered;'' 

 which can be readily done, if several 

 concentric circles have been turned 

 on the rotating-table, by making the 

 cover-glass correspond with the one- 

 having its own diameter. A number 

 of ingenious modifications have been 

 devised in this simple instrument, 

 with the view of securing exact cen- 

 tering; the simplest of them (which 

 has the advantage of being applic- 

 able at a trifling expense to any ex- 

 isting turn-table) being that of Mr.. 

 C. S. Rolfe.' But as it is often re- 

 quisite to use this instrument with 

 slides not accurately cut to size and 

 shape, or of greater breadth than the 'regulation' 1-inch, the Author is dis- 

 posed to prefer the form devised by Mr. Dunning 2 (Fig. 126). The circular 



Dunning's turn-table. 



1 Journal of the Quekett Microscopical Club," Vol. V., p. 249. 



2 Op. cit , vol. vi., p. 81. 



