176 ON MAKING USEFUL 



to show. The glass slips were of the commonest quality, selected 

 thin and flat, and cut to the exact size. The edges were not 

 ground, but the extreme sharpness was removed from them by 

 dragging one edge over another, and if this is thoroughly done it 

 is a very good substitute for ground and smoothed edges. I think 

 the plan I have described better than metal, porcelain, or glass 

 cells sealed up hermetically, as dry mounts often fail owing to 

 imprisoned moisture. One may suppose that a cell of cardboard 

 which is not perfectly air-tight would be best. However, be this 

 as it may, I found all to go well for a time, but after some months 

 I noticed some of the larger Beetles showing signs of the old 

 enemy, grease. This, of course, was fatal, so I set to work to 

 find another and I hoped a better way. I thought of a metal 

 cell, with a cover which could be removed when viewing the 

 object ; in fact, something like a small, shallow box with a lid to 

 it. The next thing was to see if such a cell could be obtained, 

 and I found that it would in the first place be necessary to have 

 special dies made. The cost, however, of these was such that it 

 was quite out of the question. Then I thought of pill-boxes, and 

 I think I have secured all the advantages wished for in a very 

 simple way, by merely affixing a pill-box of one inch in diameter 

 of the kind known as "Frank's Postal Pill-Boxes" on the centre 

 of a slip of glass, which has been previously papered; and to 

 prevent particles of paper being frayed off and getting on the 

 objects, the pill-boxes were brushed over inside and out with 

 shellac varnish or patent knotting. This very much strengthens 

 them and improves them in every way. The plan of varnishing 

 all pill-boxes used for collecting purposes is a very good one, as 

 they then last very much longer and are not readily affected by 

 damp. Mounted in this way, the objects can be readily treated 

 with the proper remedies if anything goes wrong with them, and 

 there is not the interference of the cover-glass, which is an im- 

 portant consideration, if it is wished to view the object at all 

 obliquely. 



Of all the larger species, dissections of the mouth-organs may 

 be easily made and mounted in this way. Dissections will not be 

 required of every species, but only of those typical of the genera, 

 or that show any striking pecuUarity. The very large insects 



