Dal 21 marzo al 21 giugno 2016 a Firenze, Roma, Napoli, Palermo, Padova

Mr. Lockyer on the Eclipse

Mr. Lockyer, the English astronomer, in speaking of the eclipse, says:
Cloud in Sicily, cloud in Spain, cloud in Africa. Such, at first sight, might seem to be the only result of all the observations made on the eclipsed sun of 1870; such the reception given by Nature to those who wooed her as she had never been wooed before; who approached her full of the rarest gifts which science has placed at man’s disposal. But, after all, has the oracle been silent? I think not. Dare we, however, say that the great problem of the corona, that one among the many still outstanding difficulties which the eclipse was invoked to settle, is settled? This, perhaps, would be saying too much; but still, I think, a step in advance has been made. The oracle has spoken darkly, perhaps, but it has spoken.

1870 Osservazione della Corona osservata a Catania

Disegno della corona solare fatto da Melusina Fay Peirce (1836-1923), moglie dell’astronomo Charles. Le osservazioni furono eseguite dalla villa del marchese di Sangiuliano a Villasmundo.

The system of sketching, introduced for this eclipse, is at once so simple and final, that the only wonder is, it has not been introduced before. The corona must be either solar, atmospheric, or subjective; that is, more or less built up in the observer’s eye,while this more or less depends, cateris paribus, upon the brilliancy of the undoubted solar portion. If at all stations, the stations being as wide apart as they have been this time, the drawings be similar, the corona would be undoubtedly cosmical; if dissimilar, then it would either be terrestrial or subjective; and this point could and would have been settled this time, if the weather had permitted, by arranging the observers in pairs—that is, dealing with two observers instead of a single one, and so obtaining the eye-variation. This being premised, what is the result of the very few observations, comparatively speaking, which have been made? In the first place, I submit that the fact that the corona is a compound phenomena comes out in an unmistakable way. We have, first of all, a ring some 5 min. or 6 min. high round the moon, which almost all observers alike have seen; and then we have light beyond, which some observers have seen of one shape, and some of another, now stellate with many rays, now stellate with few, now absolutely at rest, now revolving rapidly.
This, I think, is the keynote of all the observations with which I have become acquainted. I need scarcely say that it is exactly what has been predicted. First among the fortunate ones who observed the corona, with the telescope, was Professor Watson, of Ann Arbor, who took up his station at Carlentini, and appears to have been the best favored among the Sicilian observers. From his account I gather that there was an almost perfect shell around the sun, 5 min. high, and that outside this shell were less definite rays.
Next I must mention Professor Pierce, the head of one of the American parties, who observed two miles north of Catania, at a private casino of the Marchese Sangiuliano. I believe that he also saw the shell, but of this I am not absolutely certain; but he distinctly observed that the outer corona over the prominences was rosy red, although he did not see the prominences himself. A more beautiful proof of the terrestrial nature of this portion of the corona it would be difficult to imagine; for, of course, at the sun, the hydrogen, which thus tinged it, is incapable of coloring anything, as its own light is
absorbed by the transcendent brilliancy of the photosphere; while nothing would be more natural than to suppose that the light, which, in its own atmosphere, should strongly tinge any thing radially illuminated, should be that of the prominences.
But the strongest proof of the variability of the outer portion, and of the constancy of the inner portion, is afforded by the observations made on board the small fleet attempting to save the Psyche, off Aci Reale, where the eclipse was observed in unclouded splendor. Here were the ironclads, Lord Warden, Caledonia, and Royal Oak, and the tugs Weasel and Hearty, besides the Italian gunboat, Plebiscito, all within a stone’s throw of each other. In all the drawings, and many have been received, we have a ring 5 min., or thereabouts, while the outer portion is as variable as may be.
I think that if the records of former eclipses be now examined, especially Mr. Carrington’s drawing of the eclipse of 1851, and compared with the others taken at the same time, additional evidence will be gathered in favor of the compound nature of the corona, which, on the evidence now before me, I consider the great teaching of the present eclipse.

Scientific American, 1871,  vol. XXIV, n. 10, 4 marzo

scarica articolo originale