145
1858 .]
iron is, but, like tlie magnetized steel needle, they are mag-netic and polar. And these poles are irregularly dis-tributed like the “ consequent points” to which I havereferred, and this is the reason why I have used the term.
Professor Forbes, as I have already stated, was the first tonotice the effect of the BifMhom upon the magnetic needle,but he seems to have supposed that the entire mass of themountain exercised “ a local attraction” upon the needle;(upon which end he does not say). To enable future observersto allow for this attraction, he took the bearing of several ofthe surrounding mountains from the Biffelhom; but it isvery probable that had he changed Iris position a few inches,and perfectly certain had he changed it a few yards, he wouldhave found a set of bearings totally different from thosewhich he has recorded. The close proximity and irregulardistribution of its consequent points would prevent thePufi'elhorn from exerting any appreciable influence on adistant needle, as in tins case the local poles would effectu-ally neutralize each other.
( 21 .)
On the morning of the 15th the Biffelberg was swathedin a dense fog, through which heavy rain showered inces-santly. Towards one o’clock the continuity of the grajmass was broken, and sky-gleams of the deepest bluewere seen through its apertures; these would close upagain, and others open elsewhere, as if the fog werefighting for existence with the sun behind it. The sun,however, triumphed, the mountains came more and moreinto view, and finally the entire air was swept clear. Iwent up to the Gorner Grat in the afternoon, and examinedmore closely the magnetism of its rocks; here, as on theRiffelhom, I found it most pronounced at the jutting pro-
h