320 On the Common Blowpipe. 



Even a piece of the stem of a tobacco pipe can be used as a 

 blowpipe when no better means are at hand. 



In experiments requiring a long continued blast, the moisture of 

 the breath condenses in the tube in such quantities as to be inconve- 

 vientj and the best blowpipes are provided with a small chamber to 

 collect this moisture, and prevent its being forced out at the orifice 

 into the flame. 



Fie:. 2. 



Id-^ 



c 



Fig. 2, shows the parts of a blowpipe provided with a chamber 

 C. At D is a conical orifice which slips into the projection from the 

 chamber. At E is a small perforated cone, to be placed over the 

 end of D when a smaller orifice is required. 



Fig. 3. 



Fig. 3 shows the blowpipe arranged for use. 



In using the blowpipe it is highly important to be able to keep up 

 a well regulated and long continued blast. The power to do this 

 can be acquired only by practice, but the following directions, taken 

 from Shepard's Mineralogy, will facilitate the acquisition. " Closing 

 the mouth, keep the cheeks distended with air, during a number of 

 inspirations and expirations performed through the nostrils. Next 

 attempt the same with the mouth-piece of the blowpipe between 

 the lips : now as this provides an exit for the air in the mouth, the 

 cheeks will soon collapse ; to prevent this at the moment of expira- 

 tion through the nose, a sufficient quantity of air must be allowed to 

 enter the mouth to preserve their distention. By this means the air 

 in the mouth is constantly subject to the same compression and flows 

 in a uniform manner from the little orifice. Having acquired the 

 habit of keeping up a continued current of air from the blowpipe, 

 the beak is now brought within the border of the flame of a lamp or 



