276 Professor S. P. Langley [Ai^ril 17, 



intervals, and the soil at a distance seems as though strewed with 

 sheets of salt, which aids the delusive show of the mirage. These 

 are, in fact, the ancient beds of dried-up salt lakes or dead seas, some 

 of them being below the level of the ocean ; and such a one on our 

 right, though only about twenty miles wide, has earned the name of 

 " Death Valley," from the number of human beings who have perished 

 in it. Formerly an emigrant train, when emigrants crossed the con- 

 tinent in caravans, had passed through the great Arizona deserts in 

 safety until, after their half-year's journey, their eyes were gladdened 

 by the snowy peaks of the Sierras looking delusively near. The goal 

 of their long toil seemed before them ; only this one more valley lay 

 between, and into this they descended, thinking to cross it in a day — 

 but they never crossed it. Afterwards the long line of wagons was 

 found with the skeletons of the animals in the harness, and by them 

 those of men, women, and little children dead of thirst, and some relics 

 of the tragedy remained at the time of our journey. I cite this as an 

 indirect evidence of the phenomenal dryness of the region— a dryness 

 which, so far, served our object, which was, in part, to get rid as much 

 as possible of that water vapour which is so well known to be a 

 powerful absorber of the solar heat. 



Everything has an end, and so had that journey, which finally 

 brought us to the goal of our long travel, at the foot of the highest 

 peak of the Sierras, Mount Whitney, which rose above us in 

 tremendous precipices, that looked hopelessly insurmountable and 

 wonderfully near. The whole savage mountain region in its slow 

 rises from the west, and its descent to the desert plains in the east, is 

 more like the chain called the Apennines, in the moon, than anything 

 I know on the earth. The summits are jagged peaks like Alpine 

 " needles," looking in the thin air so delusively near, that, coming on 

 such a scene unprepared, one would almost say they were large grey 

 stones a few fields ofi^, with an occasional little white patch on the 

 top, that might be a handkerchief or a sheet of paper dropped 

 there. But the telescoj^e show^ed that the seeming stones were of 

 the height of many Snowdons piled on one another, and the white 

 patches occasional snow-fields, looking how invitingly cool, from the 

 torrid heat of the desert, where we were encamped by a little rivulet 

 that ran down from some unseen ice-lake in that upj)er air. Here 

 we pitched our tents and fell to work (for you remember we must 

 have two stations, a low and a high one, to compare the results), and 

 here we laboured three weeks in almost intolerable heat, the instru- 

 ments having to be constantly swept clear of the red desert dust 

 which the hot wind brought. Close by these tents a thermometer 

 covered by a single sheet of glass, and surrounded by wool, rose to 

 237° in the sun, and sometimes in the tent, which was darkened for 

 the study of separate rays, the heat was absolutely beyond human 

 endurance. Finally, our aj^i^aratus was taken apart and packed in 

 small pieces on the backs of mules, who were to carry it by a ten 

 days' journey through the mountains to the other side of the rocky 



