PRODUCTIONS OF THE HIMALAYA. 



•231 



Almost all the nodules have more or less of the metallic lustre 

 on the outside, owing to the degree of friction they have undergone. 

 But the fracture surface is always dull ; the composition being, appa- 

 rently, fine earthy. On being rubbed or cut, it recovers its polish. That 

 the absence of lustre on the fracture is dependent on its state of aggrega- 

 tion or composition, as mineralogists call it, seems further probable from 

 its extreme porousness. One specimen, by some trials, appeared to absorb 

 one-fourth of its bulk of water. 



The specific gravity of those specimens apparently most free from 

 foreign contamination, varied from 2- 21 to 2-26. There is little doubt 

 that, in the case of a mineral like graphite, the specific gravity is a valid 

 test of its purity. It is interesting, then, to compare these A^alues with 

 that generally assigned by the best authorities. Amongst the older 

 writers, there is such a range of results as warrant their rejection altoge- 

 ther. Professor Mohs, one of our best modern authorities, assigns I S to 

 2*1 as the limits — Hauy 2*089, as an actual determination. Schrader again, 

 who undertook a particular examination of the graphites from different 

 countries, states the specific gravity of English specimens, remarkably 

 pure, and one of them from Borrodale, at 2-32 to 2*46. However this may 

 be, the mountain graphite is, certainly, of inferior quality — although I 

 have succeeded in manufacturing a very tolerable pencil from it, and even 

 in cutting out a small cylinder, such as is used in the patent pencil cases. 

 It is also to be noted, that the graphite in England undergoes the prepa- 

 ratory operation of being boiled in, oil. It is possible that such a process 

 may considerably improve the quality of the mineral. 



The uses of graphite are not confined to the construction of pencils, 

 and there is a demand for very inferior qualities of the article. Advert- 

 ing to the increasing employment of steam engines, it may be safely said 



that 



