xxviii Report of the Miner alocj'ical Survey [No. 126*. 



perience, however agreeable to the deductions of science, must necessa- 

 rily excite. 



45. It is this phenomenon which has always occasioned them to be 

 objects of attention, and it is singular enough that it is also on erroneous 

 considerations connected with this phenomenon that the doubts of their 

 superior elevation have been founded. I shall include under the remarks 

 on climate, what I have to offer on the theory of the subject and the 

 arrangement of the Isothermal bands. I shall here confine myself to a 

 statement of a few of the most interesting particulars connected with 

 the occurrence of this phenomenon. 



46. It will be readily understood, that according to the season of the 

 year, the zone which is marked by snow will be of more or less extent. 

 If we take our estimate in that month in which the quantity is a mini- 

 mum, and after which there falls more than melts, we may satisfy our- 

 selves that a belt of ten to fourteen miles in breadth is distinguished by 

 this phenomenon. It is not meant that snow lies in every point of this 

 tract, but merely that within it will be found summits bearing snow all 

 the year round. The minimum elevation of this snow-bearing tract is 

 nearly in round numbers 15,000 feet, which may therefore be taken as 

 the elevation in this latitude of the curve of perpetual congelation. 

 There are, however, many spots of greater elevation perfectly bare of 

 snow, this fact is, however, connected with a different arrangement of the 

 seasons, and will be noticed in the section on climate. At all elevations 

 exceeding the above, where snow lies, it is generally quite firm, except 

 immediately after a fresh fall. 



47. Many parts of this zone have such a disposition of the surface that 

 it is quite impossible that any part of the snow which falls should 

 ever be lost, except by melting, or by evaporation. The loss from the for- 

 mer cause must be very little at elevations much exceeding 15,000 feet. 

 At 18,000 it must nearly cease altogether. The loss from evaporation will 

 doubtless be considerable under so rare an atmosphere, still however we 

 may safely conclude, that a surplus is left every year to accumulate. In 

 favorable situations, we may imagine then the depth of these snows to 

 be very great. In fact, we may suppose a case, without hazarding any 

 improbability, where they have been yearly increasing since the origin of 

 these mountains. Such supposition is calculated to give us a stupen- 

 dous idea of the magnitude of these deposits. 



