And frost remains where burning ashes glow;
O'er ice eternal sweep th' inactive flames,
And winter, spite of fire, the region claims.'
Claudian, from the Latin.
----'Snowy Ætna, nurse of endless frost,
The mighty prop of heaven.'
Pindar, from the Greek.
The height of Ætna is generally estimated at 11,000 feet above the sea. In 1755, it issued out a torrent, not of mud, as was supposed, but of snow and ice melted by the lava. The same thing happened at the volcano of Cargarossa in South America.
The celebrated Herschel, (Phil. Trans. 1801, and Nich. Jour. 1. 13), in considering the construction of the sun, infers it to be a habitable globe more magnificent than our earth, or other planets, and that its lucid substance is not a liquid nor an elastic fluid; but that it exists in the manner of luminous clouds, swimming in the transparent atmosphere of the sun, or rather of lucid decompositions taking place within that atmosphere. The Philosophical Transactions, 1795, p. 72, also contains remarks on this lucid matter. Having rejected the old terms of spots, nuclei, penumbræ, and luculi, he has substituted those of openings, shallows, ridges, nodules, corrugations, indentations, and pores. The openings are places where the luminous solar clouds are removed, which he thinks are produced by a wind or gas from the sun's body. Shallows are depressions below the luminous clouds, and are caused by the propelling gas, which produces the openings. They are tufted like masses of clouds. Ridges are elevations of the luminous clouds. The length of one of the longest was found to be 75,000 miles. They generally surround the openings. Herschel thinks it probable, from appearances, that the luminous matter is disturbed at top by the transparent elastic fluid, which issues from the openings. Nodules are small elevations of the luminous matter. Corrugations are smaller elevations and depressions of the same matter. Indentations are the dark places of corrugations. That they are not much depressed, is deduced from their visibility near the margin of the sun. They are of the same nature as shallows, and of different sizes. Pores are the low places of indentations. The doctor is of opinion, that the phenomena before described could not appear, if the shining matter were a liquid; because, by the laws of hydrostatics, the openings, shallows, indentations, and pores would be filled up. Still less could these phenomena exist with the supposition of elastic fluidity. The shining matter, he concludes, must exist in the manner of empyreal luminous or phosphoric clouds. The planetary atmosphere of the sun, its great height, its density, as inferred from the power of gravitation, which is known to be twenty-seven times stronger at the sun's surface than with us, and other subjects are also discussed. He supposes the gas to pass from the sun itself upwards to the region of the clouds, so as to generate pores, corrugations, &c. He concludes finally, that if this view of the solar appearances be well founded, there will be no difficulty in ascertaining the actual state of the sun with regard to its energy in giving heat and light.
In a paper on the "Construction of the Heavens," the doctor thinks it probable, that the great stratum called the milky way is that in which the sun is placed, though perhaps not in the centre of its thickness. The celebrated astronomer Lalande supposes the spots before mentioned to be parts of the solid body of the sun, but admits not a luminous atmosphere, but a luminous ocean. For the observations of Dr. Young, see his Natural Philosophy, and of sir Isaac Newton, his Principia, &c. Consult also Biot.