THE MICROSCOPE. 



The object is then to be placed on this balsam, and at once 

 covered with a second drop, applied in the same way as 

 the first ; in this state the slide should remain (covered to 

 exclude the dust) for two or three minutes, that the balsam 

 may have time to penetrate ; the thin glass is then to be 

 taken up between the finger and thumb, and placed gently 

 upon the balsam covering the object. The slide being now 

 neld by the nippers at one end, place the other extremity 

 over the lamp-chimney, so that the heat may be gradually 

 extended towards the object. The proof of its having done 

 so sufficiently will be that the balsam flows to the edge of 

 the thin glass, taking with it all air-bubbles from that part 

 nearest the heat. The slide is now to be turned, the heated 

 end being placed in the nippers, and the process repeated. 

 The slide should remain flat till nearly cool, when pressure 

 should be made perpendicularly with a small piece of wood 

 on the upper glass ; this Avill expel all superfluous balsam, 

 and with it all extraneous matter. Should any air-bubbles 

 remain, they generally disappear in a few days. If the 

 balsam requires hardening, place the slide on the mantel- 

 piece, the gentle heat here will prove sufficient." 



Mr. Deane recommends a composition of gelatine for 

 mounting dry or moist animal or vegetable structures, in 

 place of Canada balsam; his formula for which is as 

 follows : 



" Take of White's patent size, 6 ounces by weight ; 

 honey, 9 ounces by weight ; add a little spirits of wine and 

 a few drops of creosote; mix and filter whilst hot, to 

 render perfectly clear. Or take of pure glycerine, 4 fluid 

 ounces; distilled water, 2 fluid ounces; gelatine, 1 ounce 

 by weight ; dissolve the gelatine in the water made hot, 

 then add the glycerine and mix with care; this need not 

 be filtered. 



" It is probable that some animalcules may be better 

 shown if some moisture be allowed to remain in the 

 medium, the evaporation from which may be stopped at 

 any stage by filling round the edge of the cover with some 

 gold- size varnish, or even boiled linseed-oil. For many 

 delicate objects this has a great advantage over Canada 

 balsam, in not possessing the high refractive power of that 

 substance ; and the minute hairs and other parts of insects, 



