MOUNTING OPAQUE OBJECTS. 323 



When Canada balsam is used for mounting the specimens, 

 the precautions mentioned in page 308 must be attended to ; 

 the balsam must be very fluid, but not made so with turpen- 

 tine, and the cover must not be put on till aU the air bubbles 

 have disappeared, otherwise the little vacuities there aUuded to 

 will occur after the lapse of a few weeks or months. 



A very convenient mode of mounting opaque objects in 

 cells in the dry way is shown in section by fig. 221, where b 



- " " '- C 



Fig. 221. 



represents a thin piece of mahogany or other hard wood, 

 having a cell, c, bored out in its middle by means of a centre- 

 bit ; the hole should not extend through the entire thickness 

 of the wood, but about half way, as shown at c; the objects 

 fastened to a disc of paper or card may be secured to the 

 bottom of the cell by means of one or other of the cements 

 previously described, and a cover of thin glass, d, having been 

 placed over the hole, may be firmly fixed there by one of the 

 cements or by a layer of paper, e, gummed to it and the 

 mahogany in the manner described at page 314. 



Mr. Julius Page has made some very excellent cells of the 

 flattened tin wire employed by cabinet-makers for inlaying, 

 by bending it into a square or round shape upon a bar or 

 cylinder of wood; these he fixes to the slide by marine-glue 

 or other cement, using a large quantity on the outside of the 

 cell to form an embankment, and to prevent the gold-size 

 employed in the fastening down of the cover from entering 

 the cell where the two ends of the wire are brought into con- 

 tact. Cells so made wiU answer as well for preparations 

 mounted in fluid as for those that are dry, tin being a metal on 

 which few of the preservative solutions will act. 



In Pill Boxes. — The author's late brother, Mr. Edwin 

 Quekett, adopted a plan for mounting opaque objects, which 

 answered exceedingly well; this was to select some small but 

 21* 



