Page:Popular Science Monthly Volume 9.djvu/576

550 the serpent, it certainly receives only blood that has previously been aërated; hence we find in this animal no true aërial respiration alternating with strictly aquatic respiration.

But, though the Amia is not amphibious, and hence not to be considered in this place, nevertheless we must not omit to mention the fact that, while at present the genus is restricted within rather narrow geographical limits, it appears to have existed in Europe during the epoch known to geologists as the Middle Tertiary.

Thus there have been found at Oeningen (Switzerland), Kutschlin (Bohemia), Ménat and Armissan (France), fossil remains of Cyclurus, which has a close affinity with Amia. It is highly probable, not to say certain, that these fishes buried themselves in the mud during the dry season. The little tertiary lakes of Limagne appear to have undergone in past times alternations of drought and humidity, like the marshes of tropical and intertropical countries.

The presence in Europe of a genus closely allied to the Amia of America would seem to show that, at a relatively late period, these two divisions of the world were connected. The study of tertiary insects, to which E. Oustalet has devoted himself, and a thorough investigation of fossil fishes, would, we think, tend greatly to confirm Oswald Heer's hypothesis, according to which an Atlantis—not an historical Atlantis, as understood by Plato, but a geological Atlantis—connected the north of Europe with America toward the close of the great Tertiary epoch.



HE history of burning-mirrors of brass is known. At Rome the sacred fire was lighted with apparatus of this kind, and Archimedes fired the ships which were blockading Syracuse by concentrating upon them the sun's rays by means of a large reflector. Buffon repeated successfully the experiments of Archimedes. With a mirror of very slight curvature, consisting of a number of pieces of looking-glass, he set fire, at some distance, to fir and beech planks, melted tin and silver, and brought iron to a red heat. Saussure later accumulated, by means of superimposed inclosures of glass, the sun's heat up to a temperature exceeding that of boiling water, and Sir John Herschel repeated these experiments at the Cape of Good Hope at various times between 1834 and 1838. At the same period the French physicist Pouillet was engaged at Paris in measuring the calorific intensity of solar radiation, arriving at the conclusion that the heat emitted