660 THE POPULAR SCIENCE MONTHLY. 



fort, but the formidable descent and the ensuing desert journey were 

 before us, and certainly the reign of perpetual winter around us grew 

 as hard to bear as the heats of the desert summer had been. On 

 September 10th we sent our instruments and the escort back by the 

 former route, and, ourselves unencumbered, started on the adventurous 

 descent of the eastern precipices by a downward climb, which, if suc- 

 cessful, would carry us to the plains in a single day. I at least shall 

 never forget that day, nor the scenery of more than Alpine grandeur 

 which we passed in our descent, after first climbing by frozen lakes 

 in the northern shadow of the great peak, till we crossed the eastern 

 ridges, through a door so narrow that only one could pass it at a time, 

 by clinging with hands and feet as he swung round the shoulder of 

 the rocks to find that he had passed in a single minute from the view 

 of winter to summer, the prospect of the snowy peaks behind shut 

 out, and instantly exchanged for that below of the glowing valley 

 and the little oasis where the tents of the lower camp were still 

 pitched, the tents themselves invisible, but the oasis looking like a 

 green scarf dropped on the broad floor of the desert. We climbed 

 still downward by scenery unique in my recollection. This view of 

 the ravine on the screen is little more than a memorandum made by 

 one of the party in a few minutes' halt part-way down, as we followed 

 the ice-stream between the tremendous walls of the defile which rose 

 two thousand feet, and between which we still descended, till, toward 

 night, the ice-brook had grown into a mountain-torrent, and, looking 

 up the long vista of our day's descent, we saw it terminated by the 

 Peak of Whitney, once more lonely in the fading light of the upper sky. 



This site, in some respects unequaled for a physical observatory, 

 is likely, I am glad to say, to be utilized, the President of the United 

 States having, on the proper representation of its value to science, 

 ordered the reservation for such purposes of an area of one hundred 

 square miles about and inclusive of Mount Whitney. 



There is little more to add about the journey back to civilization, 

 where we began to gather the results of our observation, and to reduce 

 them to smelt, so to speak, the metal from the ore we had brought 

 home a slow but necessary process, which has occupied a large part 

 of two years. 



The results stated in the broadest way mean that the sun is blue 

 but mean a great deal more than that ; this blueness in itself being per- 

 haps a curious fact only, but, in what it implies, of practical moment. 



We deduce m connection with it a new value of the solar heat, so 

 far altering the old estimates that we now find it capable of melting a 

 shell of ice sixty yards thick annually over the whole earth, or, what 

 may seem more intelligible on its practical bearings, of exerting over 

 one horse-power for each square yard of the normally exposed surface. 

 We have studied the distribution of this heat in a spectrum whose 

 limits on the normal scale our explorations have carried to an extent 



