Daily National Intelligencer

FROM THE PROVIDENCE AMERICAN.
The following letter from Col. John Gibbs, (a native of Rhode Island, but now resident in New York,) to professor Silliman, and published in the Journal of Science, is highly interesting. The theory receives much confirmation from recent circumstances, of the polarity of light, i. e. that every ray of light has distinct sides, and when reflected from one mirror to another, at a proper angle, will not be again reflected, unless the north or south side of the ray be presented to the second mirror. (Vide Edinburgh Review, No. 63.) I visited the last year the mine of magnetic iron at Succasunny, belonging to governor Dickerson, of New Jersey. The mine had not been worked for a year past, and I did not descend it. The proprietor, a gentleman of distinguished science, informed me of a singular circumstance attending it, which was too important to be left unnoticed. The mine is worked at the depth of 100 feet: direction of the bed northeast and southwest; inclination nearly perpendicular. The ore in the upper part of the bed is magnetic, and has polarity; but that raised from the bottom has no magnetism at first, but acquires it after it has been some time exposed to the influence of the atmosphere. This fact, of which there is no doubt, struck me as most singular. I could not recollect any similar observation; and it is only lately I have found that Wermer had observed, that iron sand raised from the depth of 100 feet, had no magnetism. See Rees' Cyclopedia, art. Sand. I could only account for this circumstance by supposing that magnetism existed not in the interior of the earth, as was supposed, but only on the surface, and in such bodies as received this principle from atmospheric or celestial influence. The late discovery of the magnetic influence of the violet rays of light, by M. Morechini, a notice of which has since reached us, in the journal, connected with the above fact, leads me to believe that light is the great source of magnetism. A learned foreigner, * whose residence in this country has contributed much to its scientific improvement, has also informed me that other substances than metallic have been found, by compression, to be magnetic. It is well known, that the violet ray is the most refrangible, or has the most attraction to matter. But there are other rays, which Herschel, who some years since discovered them, calls invisible rays, which are still more refrangible, are next beyond the violet, when refracted, and partake of most of its properties, except that they are invisible. I have not yet seen any account of the experiments of M. Morechini, other than the notice in the Journal; but I trust I soon shall be able to determine whether those invisible rays do not possess the magnetic power as well as the violet; or perhaps possess it exclusively. As the refraction of the atmosphere, in the polar circles, is at least ten times greater than in the tropics, a greater quantity of the magnetic rays will there be separated and combined than elsewhere; and of course arises excess of magnetism. Hence the direction of magnetic bodies towards the northern and southern extreme regions. The great absorption and emission of light in the polar regions, by the ice and snow, may cause the extraordinary illumination of that country during the absence of the sun: and the emission of the magnetic rays with electricity, may, perhaps, give us the aurora borealis. The coincidence of the diurnal variation of the compass with the solar influence, deserves particular notice, and will have considerable weight on this subject. That there are many facts which cannot readily be explained by the theory of light, I shall not deny; but, in the infancy of this system, we may be allowed to hope, that future observations may enable us to remove present difficulties. One thing must be admitted, that no theory has heretofore been published relating to magnetism which has received or seems entitled to much confidence. I have no doubt that philosophy will finally determine that we owe to the solar ray, light, heat, electricity, and magnetism.
* M. Correa de Serra, Minister of the King of Portugal.