INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. G97 



and is better taken care of by its owner and his friends, than one 

 which is not thus embellished, and which shows a greater or less 

 amount of balsam irregularly distributed around the edge of the 

 cover, I will, therefore, jot down a few remarks on the ringing and 

 finishing of slides. After tlie object has been mounted in balsam 

 and the cover apjilied, it will be found that there is always a greater 

 or a less surplus of balsam which comes out from under the cover. 

 This should be allowed to dry, and when thoroughly hard it can be 

 scraped off with a knife. If a round cover has been used, the slide is 

 then centered on a turntable, and the cover cleaned with benzoic, 

 which is best done by dipping a soft linen rag in the benzole and 

 applyiug the wet place with the forefinger to the centre of the cover- 

 glass ; the turntable being revolved, the finger is quickly drawn 

 toward the edge of the cover and the rag removed. One or two such 

 wipings of the cover will be found sufficient to remove all traces of 

 balsam or extraneous dirt. The slide itself may then be wiped also 

 with benzole, and it is then ready for the application of a ring. 



The best ringing medium for balsam mounts is dammar dis- 

 solved in chloroform, because if it is inclined to run under the cover 

 it will readily mix with the mounting material without leaving a 

 visible trace behind. I find it best to apply the brush to the edge of 

 the cover almost dry, the slide on the turntable sj)iuuing rapidly 

 around, so as to make a track in which the dammar solution will 

 readily flow. The second application is to be made immediately 

 following the first, with the brush full, so that there will be a small 

 drop of solution on the end, which is allowed to touch the edge of the 

 cover without letting the brush itself come in contact with the glass. 

 This is repeated until the ring is bnilt up to the proper size. It 

 should be borne in mind, however, that in drying, the ring of dammar 

 will shrink considerably, and thus it is necessary to make another 

 application after a few hours' drying. 



Dammar or balsam dissolved in benzole or benzine is objection- 

 able, because the solution will evaporate too quickly to allow of a 

 proper building up of the ring, and if such is attempted the re^^ult 

 will be a ring full of minute air-bubbles. White zinc cement, 

 Brunswick black, asphaltum varuisli, and other coloured cements may 

 be employed to cover the first ring of dammar ; but they should never 

 be used alone, as they are sure to run in sooner or later, no matter 

 how hard tlie balsam may be. I think that the glass-like ring 

 obtained with dannuar gives a better appearance to the slide and is 

 more durable than any of the rings made with coloured cements. 



When glycerine mountings, or objects mounted in a watery 

 medium are to bo ringed, -it is necessary to first get entirely rid of 

 any glycerine which might be on the cover or slide. To do this I 

 apply a spring clip to the slide, which serves to hold the cover iu 

 position after it has been centered, and then wasli off the surplus 

 glycerine with a stream of water from a syringe. The slide is then 

 set on end to dry, and a ring of a waterproof cement is applied around 

 the cover. Such a cement may be bouglit under the name of Bell's 

 cement, the composition of wlnVli is a t^ecrct. A bitter and less 



