PRESERVATION OF NAT. HIST. SPECIMENS. 505 



passage for moisture, and closed bookcases for the same reason offer a very 

 doubtful protection to books. Certain bindings are very absorbent, and 

 become readily mildewed. Mr. E. H. Aitken, a keen observer of these 

 things, kept his books in an open case in the middle of a room. To arrest the 

 attacks of insects he coated his cloth-bound covers with a thin solution of 

 copal varnish in turpentine, which maintained the new appearance of the 

 cloth and arrested deterioration. Very valuable books can only be preserved 

 in India iu the special boxes just described. Of insecticides there seem to be 

 a liberal provision whose properties are fairly well known. Petrol in a piece 

 of sponge produces a deadly but inflammable atmosphere, Naphtbalin is 

 largely used, but it discoloui"s brass, copper and the precious metals ; dissolved 

 in petrol it may be applied with success with a fine dropping tube to worm 

 holes in books. Camphor is less effective than naphtbalin. Mineral oil is 

 fatal to all parasitic insects but not to all fungoid growths. 



In conclusion, I would add a few remarks on the joints of boxes or cases. 

 Two surfaces, however narrow, in close contact produce an airtight joint. 

 There is therefore no advantage to be gained by ribs or recesses which com- 

 plicate the manufacture of uniform and other cases. Fine felt on a joint may 

 filter the air but it is nob airtight and will not arrest moisture. Cork is only 

 airtight under considerable pressure, and to get a level bearing all round a box 

 would involve much work on the cork. A true metal and metal joint can only 

 be produced with the aid of machines. A line of India-rubber cord cemented 

 to one surface of a joint will become really airtight with very little pressure, 

 but it has an unfortunate way of sticking to both surfaces, and an application 

 of graphite is only a partial remedy. The merits of any vessel, for which aii-- 

 tightness is claimed, may be easily tested by means of a cycle air pump and a 

 small length of tube attached to the bottom of the vessel. A smoking cigarette 

 passed round the joints will at once detect any leakage by the effect of the 

 escaping air on the smoke. 



This subject might be ex tented to the volume of the book, for it touches 

 many important matters in daily life and commerce. It offers an explanation 

 for the deterioration of large quantities of meichandise in India ; it makes 

 clear the cause of accumulation of dust iu a closed empty building which may 

 remain clean outside, and it suggests methods of storage and preservation of 

 goods in the Tropics which will, some day, effect important economies. 



THE PRESERVATION OF PINNED INSECTS IN THE TROPICS, 



Mr. H. Maxwell Lef roy gave me the following information : — 

 The msect collections at Pusa are stored in over 2,000 store boxes ; they 

 have been gradually built up during the past five years under extremely un- 

 favourable conditions as regards housing, transfer from place to place, supervi- 

 sion and so on, but are now permanently housed in the Pusa Laboratory. 

 Below wo give our experience of keeping collections of pinned insects unde,. 

 the conditions obtaining in India, 



