80 THE MICROSCOPE. 



Mr. Thomas Boys, in giving directions for mounting objects in 

 Canada balsam, says, the first thing to be considered is the apparatus 

 required. 



1st. A small single-wick oil-lamp, having a glass chimney about 

 four inches long ; the flame to be about the size of that in a hand- 

 lantern : a spirit lamp will do even better. 



2d. Slips of glass of required size, and small pieces of thin glass to 

 cover the object, all well cleaned. 



3d. A pair of nippers to hold the glass-slips. 



4th. A pointed iron-piercer in a wooden handle. 



5th. A bottle containing the clearest Canada balsam, diluted with 

 the best spirits of turpentine to a consistency allowing it to drop 

 readily from one end of the iron-piercer, or Mr. Gorham's cementing- 

 pencil. The preceding articles being spread before you ready for use, 

 and the object to be displayed well examined for choice of position, 

 and cleaned if necessary, fix the glass-slip in the nippers, dip the 

 piercer into the balsam, and withdraw a full-sized drop to place upon 

 the slide. The centre of the slide should now be rested across the 

 chimney of the lamp until the balsam begins to spread, when it must 

 be immediately withdrawn. 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 held 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 nip- 

 pers, and the process repeated. The slide should remain flat till nearly 

 cool, when pressure should be made with a small piece of wood perpen- 

 dicularly on the upper glass ; this will 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 harden- 

 ing, place the slide on the mantel-piece, the gentle heat from which 

 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, 



