On the use of the Blow-pipe. 113 



ihe paste had been repeatedly dried, (without burning,) 

 and as often restored to a suitable consistence by fresh 

 addition of gum water ; and if so, it must be owing to 

 these additions separating the particles more and more, 

 and thereby lessening the communication of heat from 

 particle to particle down the cone. The minutest frag- 

 ment I could obtain by the hammer, or by rubbing toge- 

 ther two sharp edges of large fragments — although at- 

 tached to the extremity of a cone nearly as acute as a 

 needle's point — was affected, by the greatest heat I could 

 produce, if at all, in no other way than the rounding of 

 its points and edges. We may therefore consider this 

 substance as fusible only in a state of powder. 

 No. 15. Sappare — (Litchfield, Conn.) From a single experi- 

 ment, which I have not had leisure to repeat, I infer that 

 this substance is infusible before the common blowpipe. 

 The apex of a very acute cone was not perceptibly al- 

 tered. 

 From the experiments of Mr. Smithson, and from those 

 stated above, it is obvious that the power of the common 

 blow-pipe is greatly extended ; but it remains to be ascertain- 

 ed whether its field of usefulness, as a means of discriminating 

 between substances of various composition, has been equally 

 or at all enlarged. There are now, as respects the blow-pipe, 

 two well-defined boundaries in the mineral kingdom ; and 

 what do we gain by merely approximating these boundaries 

 a little ? This approximation, however, is not all we are able 

 to accomplish : we may, I conceive, erect a new wall of parti- 

 tion quite as prominent as those which now exist. Hitherto 

 minerals were divided, in relation to this instrument, into 

 three classes, namely — 



1st, such as are fusible per se. 

 2d, such as are fusible only with addition ; and 

 3d, such as are infusible even with fluxes, 

 15 



