24 



MINERALS AND GEOLOGY 



be examined in a similiar manner. In these experiments the begin- 

 ner must be careful not to operate on fragments of too large a bulk- 

 The smaller and more pointed the subject submitted to the flame, the 

 easier and and more certain will be the experiment. 



In out-of-the-way places the common form of blowpipe described 

 above is frequently the only kind that can be obtained. It answers 

 well enough for ordinary experiments, but the moisture which col- 

 lects in it by condensation from the vapour of the breath is apt to be 

 blown into the flame. This iuconvenience is remedied by the form 

 of construction shown in the annexed figures, in which the instru- 

 ment consists of two principal portions, a main stem closed at one 

 end, and a short tube fitting into this at right angles near the closed 



extremity. The short tube is 

 also commonly provided with a 

 separate jet or nozzle of platinum. 

 In this case, the jet can cleaned 

 by simple ignition before the 

 blow-pipe flame, or over the 

 flame of the spirit lamp. In the 

 variety of blow-pipe known as 

 "Black's Blowpipe," FIG. 27, the 

 main tube is usually constructed 

 of japanned tin-plate, and the in- 

 strument is thus sold at a cheap rate. Mitscherlich's Blowpipe, FIG. 

 29, consists of three seperate pieces which fit together, when not in 

 use, as shewn in FIG. 28. This renders it as portable as an ordinary 

 pencil-case. FIG. 30 represents Gahn's or Berzelius's Blowpipe, with 

 a trumpet shaped mouth-piece of horn or ivory as devised by Platt- 

 ner. This mouth-piece is placed, of course, on the outside of the lips. 

 It is preferable to the ordinary mouth-piece, but is not readily used 

 by the beginner. In length, the blowpipe varies from about seven- 

 and-a-half to nine inches, according to the eye-sight of the operator. 



In addition to the blowpipe itself, and the forceps described above, 

 a few other instruments and appliances are required in blowpipe 

 operations.* The principal of these comprise : a few pieces of plati- 



*It will of course be understood, that merely a slight sketch of the application of the blow- 

 pipe is given in these pages. Hence only the more necessary operations, instruments, &c. 

 are alluded to. For fuller information, the author's BLOWPIPB PRACTICE (Copp and Co, 

 Toronto) may be consulted. 



FIG. 27. FIG. 28. FIG. 29. FIG. 30. 



