138 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Dry Mounts for the Microscope. — Mr. A. W. Waters sends us 

 the following remarks suggested by the note on Professor Hamilton 

 Smith's paper in the last number of the Journal : * — 



Having mounted several thousand specimens of Bryozoa and 

 other objects in dry mounts, it seems advisable to put the experience 

 thus gained on record, even though there is no claim to any new 

 observation or any important fact observed. Unfortunately it has 

 been necessary to remove a large number of them several times, and 

 in consequence they have been subjected to the severest test of dura- 

 bility, for probably anything which stands the carelessness of Italian 

 railway porters may be considered durable. 



All are mounted on glass slips, as this enables both sides of an 

 object to be examined, and they are protected from dust by the cover. 

 Wood slips, which are used by many collectors, are found too liable 

 to warp when old, and the objects are thus damaged or broken. This 

 can be seen in some of the valuable slides in the British Museum. 

 With small cells there are few difficulties, but with deep cells there 

 is great danger of sj)ringing, and we may safely conclude that those 

 which after being made a few years stand railway journeys the best 

 may be considered the most durable and most suitable for museum 

 specimens, so as to be available for reference in 50 or 100 years. 

 Some of the specimens referred to are large colonies mounted in glass 

 " built" cells, some as much as half an inch deep, mostly fastened on 

 with gold size, which should be rather thicker than that used for 

 attaching the cover, and with these cases of springing in consequence 

 of percussion have been very few, and these few cases have been the 

 result of special circumstances ; on the other hand, with some made 

 with zinc varnish, several cases occurred, and the experience thus 

 gained proves that zinc varnish soon becomes too brittle. Trial has 

 been made of large zinc and other metal rings which have been care- 

 fully roughened with the file, but the results have been so unsatisfac- 

 tory that all metal rings are now discarded as being the most liable 

 to leave the slide. Ebonite rings have stood well, but indiarubber 

 rings about f inch in diameter have given the best results, but these 

 are not available for deep moimts, as they are not made much thicker 

 than i of an inch. For still smaller things paper and card rings, 

 which can be bought for the purpose, for a very small sum, have been 

 employed, and in all these cases it is advisable to keep a moderate 

 stock on hand, of various sizes, as thus the varnish or cement has time 

 to dry, and there is less danger of the object becoming attached at 

 the side, if left free ; but, where it can be done, it is well to attach the 

 object with a spot of cement in the centre of the cell. 



Some shellac rings, similar to those mentioned by Mr. Smith,f 

 have been used for some years, but experience has shown that it is 

 well to run gold size round these after they have been mounted and 

 cooled, as otherwise they become too brittle ; but with these rings, 

 which are attached by melting the shellac covering the ring, there is 

 however a danger of small crystals forming inside, caused by the 

 vaporization of the shellac when heated. 



* See this Journal, iii. (1880) p. 1038. f Ibid., p. 1039. 



