I
��ill fact, the heavier npparatiii wus not carried above the mountain camp.
The view from the very siimiiiit w»s over number- less peaks on the west to an horizon, Rtty miles away, of unlinown mountain-lops; t^r, with llie exception of the raat ridge of Mount Tyndall, and one or two less conspicuous ones, these summits arc not Iidowd to fame: and, wonderful as the view may be, all the charm of association with human Interest which we Bud In the mountain landscape of older lands la here taclcing. It was impossible not to be impressed with the savage solitude of this desert of the upper air. isirom man and his works; hut I turned to the study of Uie speciiil things connected with my mis- sion. Down far below, the air seemed filled with reddish dust that looked like an ocean. This dust Is really present everywhere 1 1 have found it in the clear air of , Etna); and, though we do
\ not realize its presence In
\ looking up through it, to one \ who looks down on It, the \ dwellers on the earth i \ indeed like cr»
bottom of a troubled We had cer- tainly risen towards the surface; for shout us
��\
���to study Llie dtflerences between his rays at the ■ face, and at the bottom of that turbid sea whM we had left the rest of mankind. We descended the peak, and hailed with joy the first arrival of out mule-trains with the requisite apparatus lain camp, and foimd that It had suffered less tbaa ' might be eitpecled, considering the pathless character of the wilderness. .We went to work to build piers, and mount telescopes and siderosiats, En the scene shown by the next illustration on the screen, taken , from a sketch of my own. where these rocks in immediate foreground rise Ut thrice the height ofV St. Paul's. We suffered from cold (the Ice formini^ three Inches deep in the tents at night) and frottl mountain sickness; but we were too busy t much attention to bodily comfort, and worked wltk 1 desperate energy to utilize llie remaining g days, which were ail too short.
Here, as helow, the sunlight entered a darkened tent, and was spread Into a spectrum, which waa explored lliroughont by the bolometer, measuring on the same separate rays which we had studied below in the desert, all of which were different up here, sJi having grown stronger, hut in very different propor- tions. On the screen is the spectrum as seen in tfae desert, drawn on a conventional scale, neither pris- matic nor normal, but such that the Intensity of the I energy shall be the same in each part, as It is repr»-V sented here by these equal perpendicular Id eveiyjfl color. Fix your attention on these three as typM, t and you will see better what we found on the moun- tain, and what we Inferred as to the slate of thinp elill higher up, al the surface of the aerial sea.
You will obtain, perhaps, a clearer idea, however, from the following statemenl, where I u exact figures used lu calculation, but round nanl bers, to illustrate the process employed. I may pra
mise that the visible spectrum t ~^^ from H (in the extreme blue) to
~"~--^- . the deepest red), oi
"^■^" ~ {tlie I
of forty hundrc
��deep Tiolet-blue as I have never seen in Egypt or Sldly: and yet even this was not absolulely pure, for, separately invisible, the existence of fine parti- cles could yet hu inferred from Uieir action on the light near the sun's edge; so that even here we had not got absolutely al>ove that dust-shell which seems to encircle our whole planet. But we certainly felt ourselves not only In an upper, but a different re- gion. We were on the ridge of the continent; and the winds which lore by had little in common with the air below, and were bearing past us (according to the geologlstsi dust which had once formed part of the soil of China, and been carried across the Paciflc Ocean: for here we were lifted Into the great encircling currents of the glol>e, and, 'near to the sun In lonely lands,' were In the right conditions
���D At yAB,oi,» ai.™fd«s. "»"« ■ length) t
near 80. All I low 80, to light, is the Invisible infra-red spectrum. Ni the shaded curve above the spectrum represent* t amount of energy in the sun's rays at the foot fl the mountain, and was obtained in this way: your attention for a moment on any single ptrt 4 the spectrum; tor instance, that whose waTe-leD{^~ Is 00. If the heat In this ray. aa represented by U bolomeler at the foot of the mountain, was (let u suppose) 2°, on any arbitrary scale we draw a verlic«l line, twn inches or two feel high, over that part of the siiecti'iim. If the heat at another point, such fta 4Q^ were but t°. a line would lie drawn there a quftt of an inch high; and so tin, till these vertical V mark out the shaded parts of the drawing, the b and depressions in whose imtllne correspond i 'cold bands' already spoken of. Again: If oi
��� �
