1880.] 



MICKOSCOPICAL JOURN^AL. 



123 



start the covering glass, and rapid 

 destruction of the slide follows. I 

 have found it necessary, therefore, 

 to ran a ring of some tough mate- 

 rial around the covering glass to 

 protect it, my efforts being directed 

 to discovering a material that would 

 give the necessary strength, that 

 can be easily handled, so as to make 

 a neat tinisli. I have found that 

 the best results can be obtained by 

 the use of a thick, copal, furniture 

 varnish, what is known as rubbing 

 varnish. As I have not seen the 

 use of it mentioned in print, it may 

 be new to some readers, and i 

 therefore give the results of my 

 experience. 



I use the thickest, finest varnish 

 I can procure, and put enough 

 dragon's blood in the bottle to 

 give it color, without destroying its 

 transparency. It should be so thick 

 that a small drop will not flow from 

 the camel's hair brush. The older 

 it is, the better. 



The slide having been cleaned of 

 superfluous gum or balsam, should 

 have a little shellac varnish run 

 around in the angle formed by the 

 covering glass and the slide, to pre- 

 vent the colored varnish from run- 

 ning under the cover in the subse- 

 quent operations. When this is dry, 

 which will be in a few minutes, tne 

 slide is mounted on the turn-table, 

 and a suflSciency of the varnish 

 "dobbed" around the edge of the 

 covering glass, extending over the 

 slide. The turn-table is then put 

 in rapid revolution, and with the 

 point of a knife applied to the 

 glass, first outside on the slide, and 

 afterwards inside on the covering 

 glass, a ring is spun, which may be 

 made as narrow as is desired, and 

 with its rounded top extending 

 above the covering glass. I find it 

 very easy to turn a perfectly sym- 

 metrical ring. 



The slides are laid aside in a dry 



place for at least a week to harden, 

 when the superfluous varnish can 

 be cleaned ofi: from the glass, with 

 a bit of soft linen rag, and rotten 

 stone and water, rubbing the whole 

 mount gently, with circular strokes. 

 This removes the su])erfluou8 var- 

 nish from the glass, to the edge of 

 the ring, leaving it with a clean, 

 circular edge, and at the same time 

 rubs down any inequalities which 

 may exist in the ring itself. After 

 this, wash the slide well in fresh 

 water with a soft brush to remove 

 all traces of the rotten stone, and 

 gently dry it with a soft cambric 

 handkerchief. When it is dry, a 

 few circular strokes with dry cam- 

 bric on the end of the finger, will 

 give the ring a serai-polish, which 

 leaves it with a very neat finish. 



I usually clean the whole slide 

 with the rotten stone and water, so 

 that when it is dried, and gently 

 wiped, it is ready to receive the 

 label. The whole process is quite 

 expeditious, and the results are so 

 satisfactory, in the permanence and 

 finish of the slides, that I am con- 

 fident if any one gives it a fair 

 trial, it will supersede all other 

 cements for a like purpose. W. 



OoYer-GIasses. 



Your correspondent " R, B. jr." 

 in April number, p. 68, writes : 

 '' There seems to be no good reason 

 why dealers should not furnish 

 cover-glasses accurately assorted as 

 to thickness," There is one good 

 reason, neither "R. B. jr." nor other 

 purchasers will be willing (except 

 in special cases) to pay the extra cost 

 of measuring each piece of glass ; 

 " R. B. jr." can do that himself, or 

 he must pay some one to do it for 

 him. To obtain 100 covers y^^^ of 

 an inch will require, at the best es- 

 timate, the measuring of 500. This 

 will take time, and time is money, 

 to dealers as well as to opticians. 



