Correspondence. Ill 



namely, that in E. and SE. aspects, where the sun's rays exercise their 

 greatest power, the mountains are undergoing •visible and rapid decay, 

 more or less rapid in different places, according to aspect and composi- 

 tion ; when the felspar predominates, more slowly ; when the mica 

 abounds, more rapidly ; the iron of the mica oxidizing seems to cause it 

 to decompose faster than the felspar; in many places the mica crum- 

 bled on the pressure of the hand, and had assumed a kind of clayey 

 consistence : whether the solar ray be homogeneous, or composed solely 

 of light, heat being engendered on the earth's surface, or whether it be 

 heterogeneous, composed both of light and heat, it seems to be a power- 

 ful agent in the decomposition of mountains : may not this be the rea- 

 son why Eastern shores are usually less precipitous than Western? 



In the deep abysses of the Snowy range there is apparently a Solfa- 

 tara in a constant state of activity. I once myself witnessed it from 

 the plains at Silleegoong throwing up vapour to a vast height, which 

 feathered off at the top like the water in a fountain. That it could be 

 nothing but a Solfatara seems evident from the perpendicular column 

 which rose and fell by fits, as might be expected from vapoury ebulli- 

 tion ; this continued for half an hour at least. That the action of this 

 Solfatara is permanent, under different degrees of intensity, may be 

 inferred from the fact, that a cloud is constantly seen in one direction 

 moving east from the top of the mountain, particularly during the cold 

 weather. It is usual, I believe, at Darjeeling to account for these ap- 

 pearances by saying it is snow drift ; but the objections to this are, first, 

 that snow drift would not be constant in direction, and that the perpen- 

 dicular column, rising and falling by fits, could hardly be snow.* 



Secondly, the precipices of the range when this vapour ascends are, 

 when viewed at sunrise perpendicular, and of frightful depth, where 

 no snow could lie, to be the subject of drift. In the range between the 

 snow and Darjeeling there stands the truncated cone of an extinct 

 volcano, hitherto unobserved ; a fact of itself affording strong induce- 

 ment to believe that in the depths below there may be, as I conjecture, 

 a Solfatara, or volcanic vent. 



KlSSONEGUNGE, . 



near Rungpore, Feb. 6th, 1841. 

 * This appearance is probably occasioned by the condensation of vapours by the 

 low temperature of the peak. The effect is always produced on that side of the 

 summit which is sheltered from currents that may at the time exist in the atmos- 

 phere, modified by the action of the sun's rays on the peak itself. But this expla- 

 nation will scarcely account for the intermittent character of the vapour, which 

 may however be occasioned by observing it through a great horizontal distance.— 

 Ed. Cal. Jour. Nat. Hist. 



