1842.] of the Himmalaya Mountains. cxxi 



Indurated talc, (Government Collection,) 2.77 



Ditto, a second specimen, 2.7765 



All these had precisely the same degree of hardness. 



262. The dolomite has been equally well discriminated, and correctly 

 fixed by the Professor. The accounts of previous writers only serve to 

 confound the student with tenfold perplexity, from which he is only 

 extricated by his clear views, and precise determinations. That they 

 will very much tend to raise the character of a science, which till his 

 book appeared was but empiricism, is obvious. Of their utility to the 

 student I can myself bear witness, and this very mineral, as well as 

 calcareous spar affords many instances. The limits of the latter are fixed 

 at 2.5 and 2.8, of the former at 2.8 and 2.95. The following are some 

 determinations I made : — 



Grey compact dolomite, . . . . 2.826 Pass, road to Bagsar 



above Belowree. 



Greyish white dolomite spar, . . . . 2.850 Goorung. 



Yellowish grey ditto, 2.99 Bed of Mahepore. 



Dolomite spar large rombohedrals, . . 2.83 Shor Gorung. 



Compact dolomite, purple, . . . . 2.83 Gungolee Hat,h. 

 Of these the third only exceeds the limits, and this by so small a quantity, 

 that it is very likely a revision would bring it equally with the others 

 under those limits. The veins of purplish brown calcareous spar, which 

 are found in the Gungolee dolomite, have the external characters of 

 dolomite spar quite perfect ; that is to say, pearly lustre, opacity, and 

 curved or ill-defined cleavage. Being also contained within a mag- 

 nesian rock, I naturally placed it amongst the specimens of dolomite, but 

 in determining its specific gravity as one of the above list, I found it to 

 be only 2.67. A re- examination and the test of acids satisfied me, 

 that it was really calcareous spar. This is one amongst a hundred 

 instances in which external characters alone are found perfectly in- 

 efficient to discriminate minerals, nor is there any thing in the history 

 of science more truly surprising than the pertinacity with which mine- 

 ralogists have hitherto resisted putting their system on the secure basis 

 of numerical determination. 



263. Below the mine, very beautiful massive talc of a snowy white- 

 ness occurs, mixed with unequally white crystalline dolomite. The for- 

 mer is, however, intermixed by rents or fissures, preventing the acquisi- 



R 



