OF CENTRAL CANADA PART I. 33 



ned on charcoal, but in other cases it is more convenient to employ a 

 piece of platinum wire as a support. One end of the wire may be 

 inserted into a cork or special handle, or, if the wire be from 2J to 

 3 inches in length, it may be held in the naked fingers, as platinum 

 conducts heat very slowly. The other end is bent into a small loop 

 or ear. This, when borax or phosphor-salt is used, is ignited by the 

 blow-pipe flame, and plunged into the flux, the adhering portion of 

 the latter being then fused into a glass. If a sufficient portion to 

 fill the loop be not taken up at first, the process must be repeated. 

 With beginners, the fused glass is often brownish or discoloured by 

 smoke, but it may be rendered clear and transparent by being kept 

 in ignition for a few moments before the extreme point of the flame, 

 the carbonaceous matter becoming oxidized and expelled by this treat- 

 ment. When carbonate of soda is used, a small portion of the flux 

 must be moistened and kneaded in the palm of the left hand, by a 

 knife-point or a small spatula, into a slightly cohering paste, which 

 is placed on the loop of the wire, and fused into a bead. Whilst 

 hot, the bead is transparent, but it becomes opaque on cooling. The 

 portion of test-matter added to a glass or bead, formed by these rea- 

 gents, must be exceedingly small, otherwise the glass may become so 

 deeply coloured as to appear quite black. In this case, the colour 

 may be observed by pinching the bead flat between a pair of forceps, 

 before it has time to cool. It is always advisable, however, in the 

 first instance, to take up merely a minute particle or two of the test- 

 substance, and then to add more if no characteristic action be obtained. 

 The glass, in all cases, must be examined first before an oxidating 

 flame, and its colour observed both whilst the flux is hot, and when 

 it has become cold ; and, secondly, it must be kept for a somewhat 

 longer interval in a good reducing flame (Fig. 33), and its appearance 

 noted as before.* With certain substances (lime, magnesia, &c.) the 

 borax and phosphor-salt glasses become milky and opaque when satu- 

 rated, or when subjected to the intermittent action of the flame the 

 latter being urged upon them in short pufis, or the glass being moved 

 slowly in and out of the flame a process technically known as 

 flaming. 



* The colour of the glass ought not of course, to be examined by the transmitted light of the 

 lamp or candle flame. Strictly, it should be observed by daylfght. 

 4 



