Frozen mercury cannot be touched without experiencing a sensation similar to that of an ignited body, although directly opposite to heat.
[3] A writer of the last century remarks, that "he cannot possibly admit the sun to possess the least manner of heat, but rather to contain the capabilities of fire, like a stick, or a flint, though with a faculty of expressing it, by its own action, which the others have not. I imagine its beams not to be hot, in their rectilineal direction, but productive of this effect, from reflection, only. If the rays of the sun were fire, in the first instance, those consequences would naturally follow, that our friend and correspondent Tria so well describes in his Day of Judgment, 'The rivers were dried up, and liquid ore supplied their burning channels. The clouds were turned to fire, and shot through the astonished sky. The air was flame, and breathing was no more. The firmament was melted down, and rained its sulphur o'er the prostrate globe, &c.' The sun emanates light only, in the direct line, but owes its heat to reflection. We feel it, therefore, more intensely, in a valley, than on a hill. Why are the Alps and Pyrennees crowned with eternal frosts, while the shepherds, with their flocks, are sheltering their scorching heads from the heat of the sun, at the foot of them? Why do the upper regions of the air shower down their hail and snow, to be thawed and melted here below? Why shall a lens of ice receive the rays above, so coldly, and transmit them so intensely hot, beneath? Why is it warmer, in summer, though the sun is farther off, than in winter, when 'tis so much nearer to us? Because of our situation, in regard to it, only. In the first case the rays are vertical, in others lateral; and perpendicular reflections are stronger, than oblique ones. We judge of fire above, from what we feel below, &c."
The summit of Ætna, notwithstanding the fire of the volcano, is covered almost all the year with snow. Fazello, speaking of this says, that "this region extends nearly twelve miles; and, even in summer, is almost perpetually covered with snow, and extremely cold: which is the more wonderful as the summit continually produces, nourishes, and pours forth flames amid the ice and snow with which it is enveloped." Solinus says, "Ætna, in a wonderful manner, exhibits snows mixed with fires; and retains every appearance of the severest winter, amid her vast conflagrations."
Silius Italicus, and Claudian, and Pindar, who lived 500 years before the Christian era, bear testimony to the antiquity of this fact.
'Where burning Ætna, towering, threats the skies,
Mid flames and ice the lofty rocks arise,
The fire amid eternal winter glows,
And the warm ashes hide the hoary snows.'
Silius Italicus, from the Latin.
'Amid the fires accumulates the snow,