Professor Forbes, as I have already stated, was the first to notice the effect of the Riffelhorn upon the magnetic needle, but he seems to have supposed that the entire mass of the mountain exercised "a local attraction" upon the needle; (upon which end he does not say). To enable future observers to allow for this attraction, he took the bearing of several of the surrounding mountains from the Riffelhorn; but it is very probable that had he changed his position a few inches, and perfectly certain had he changed it a few yards, he would have found a set of bearings totally different from those which he has recorded. The close proximity and irregular distribution of its consequent points would prevent the Riffelhorn from exerting any appreciable influence on a distant needle, as in this case the local poles would effectually neutralize each other.
FOOTNOTES:
[A] Now called, in the Federal map, the 'Grenz glacier.'—L. C. T.
[B] I take this name from Studer's map. Sometimes, however, I have called it the "Breithorn glacier."
(21.)
MONT CERVIN AS CLOUD-MAKER. 1858.
On the morning of the 15th the Riffelberg was swathed in a dense fog, through which heavy rain showered incessantly. Towards one o'clock the continuity of the gray mass was broken, and sky-gleams of the deepest blue were seen through its apertures; these would close up again, and others open elsewhere, as if the fog were fighting for existence with the sun behind it. The sun, however, triumphed, the mountains came more and more into view, and finally the entire air was swept clear. I went up to the Görner Grat in the afternoon, and examined more closely the magnetism of its rocks; here, as on the Riffelhorn, I found it most pronounced at the jutting prominences of the Grat. Can it be that the superior exposure is more favourable to the formation of the magnetic oxide of iron? I secured a number of fragments, which I still possess, and which act forcibly upon a magnetic needle. The sun was near the western horizon, and I remained alone upon the Grat to see his last beams illuminate the mountains, which, with one exception, were without a trace of cloud. This exception was the Matterhorn, the appearance of which was extremely instructive. The obelisk appeared to be divided in two halves by a vertical line drawn from its summit half way down, to the windward of which we had the bare cliffs of the mountain; and to the left of it a cloud which appeared to cling tenaciously to the rocks. In reality, however, there was no clinging; the condensed vapour incessantly got away, but it was ever renewed, and thus a river of cloud had been sent from the mountain over the valley of Aosta. The wind in fact blew lightly up the valley of St. Nicholas charged with moisture, and when the air that held it rubbed against the cold cone of the Matterhorn the vapour was chilled and precipitated in his lee. The summit seemed to smoke sometimes like a burning mountain; for immediately after its generation, the fog was drawn away in long filaments by the wind. As the sun sank lower the ruddiness of his light augmented, until these filaments resembled streamers of flame. The sun sank deeper, the light was gradually withdrawn, and where it had entirely vanished it left the mountain like a desolate old man whose
"hoary hair
Stream'd like a meteor in the troubled air."
For a moment after the sun had disappeared the scene was amazingly grand. The distant west was ruddy, copious gray smoke-wreaths were wafted from the mountains, while high overhead, in an atmospheric region which seemed perfectly motionless, floated a broad thin cloud, dyed with the richest iridescences. The colours were of the same character as those which I had seen upon the Aletschhorn, being due to interference, and in point of splendour and variety far exceeded anything ever produced by the mere coloured light of the setting sun.