184 FAUNA ANTIQUA SIVALENSIS. 



embedded high, above in a mass of snow. But a descent, so 

 to speak, of the snow zone could only occur in two ways, 

 either by the line of perpetual snow being actually lowered 

 to the level of the sea, or, supposing it to maintain a constant 

 mean height, by an elevation of the mountain belt into the 

 snow zone ; either of which would produce, in appearance, 

 the same effects. 



Now, in regard to the first supposition of the lowering of 

 the line of perpetual snow, the conditions which regultite the 

 limits of that line are only very imperfectly understood, but it 

 may safely be asserted that there are no grounds to believe, so 

 far as oui- knowledge at present goes, that it oscillates more 

 than the mean temperature of a place does ; and the variation 

 in this case does not extend beyond a few degrees of Fahr. 

 Humboldt found that in the Andes, under the crater, the 

 oscillation of the line of perpetual snow does not exceed thirty 

 fathoms. In the Himalayah Mountains the present elevation of 

 the line of perjjetual snow is a huge anomaly, the plane being 

 upwards of an English mile in excess of the amount yielded by 

 calculation, with a formula for the latitude and height above 

 the sea.' If, therefore, we suppose that the pieces of timber 

 mentioned by Mr. Traill got envelojped in an avalanche by 

 a lowering of the zone of perpetual snow, it would necessarily 

 be implied that the plane of congelation was formerly more 

 elevated, and would involve a still greater irregularity than 

 the enormous extent at present ascertained, a position which 

 it would be unphilosophical to admit, except on the strongest 

 grounds. 



On the second supposition, that the mean altitude of the 

 plane of congelation is nearly constant, and that the moun- 

 tains have been elevated into the snow zone, the instance of 

 the enveloped timber would admit of two explanations ; either 

 that it belonged to the age when the Himalayah Mountains 

 had their elevation increased by the Sewalik and Tibet up- 

 heavements or that the tract on which it grew had been 

 subsequeiitly raised up into the zone of congelation. That 

 these mountains, before their summits attained their present 

 elevation, were clothed with forests high up on the tract 

 which is now covered with perpetual snow, is but consonant 

 with the course of nature to suppose ; and wood once en- 

 veloped in a snow bed would retain a freshness unim- 

 paired for countless ages ; we might, therefore, in a piece 



Feet 

 ' Perpetual snow level Niti Pass, Lat. 31° . . . 17,000 

 Calculated heiglit of ditto by Professor Leslie's formula 



forLat. 31° 11,253 



Difference 5,747 feet 



