and that heat is evolved; but this is not the case with tin stone or oxide of tin.

In the preceding article, I have pointed out a probable cause of the increase of temperature in the waters of the salt mines at Bex, in Switzerland, which had not before been noticed.

On the whole, however, making every allowance for errors from various causes, the evidence for a considerable increase of heat with the increase of depth in mines appears to be established, though the amount of that increase remains to be ascertained.

Humboldt states that, from observations made in mines and caves in every zone, it is proved that the heat of the earth is much greater than the mean temperature of the atmosphere at the same places.

ON THE SURFACE OF THE MOON.

GEOLOGISTS have not hitherto regarded with due attention the physical structure of the moon it is the only planetary body placed sufficiently near us, to have the inequalities of its surface rendered distinctly visible with the telescope. Attendant on the earth, and having the same quantity of solar light, and nearly the same density, we may reasonably infer that the mineral substances of which it is composed do not differ essentially from those on the surface of our own planet. Astronomers now generally admit that the moon is surrounded with a very clear atmosphere; but which is so low, that it scarcely occasions a sensible refraction of the rays of light when it passes over the fixed stars. Many of the dark parts of the moon, particularly the part called Mare Crisium, appear to be covered with a fluid, which may probably be more transparent and less dense than water, as the form of the rocks and craters beneath it are seen, but not so distinctly as in the lighter parts of the moon's surface. To examine the moon with a reference to its external structure, the defining power of the telescope should be of the first quality, sufficient to show the projections of the outer illuminated limb as distinctly as they appear when the moon is passing over the disk of the sun, during a solar eclipse. With such a telescope, and a sufficient degree of light and of magnifying power, almost every part of the moon's surface appears volcanic, containing craters of enormous magnitude and vast depth: the shelving rocks, and the different internal ridges within them, mark the stations at which the lava has stood and formed a floor during different eruptions; while the volcanic cones in some of the craters resemble those formed within the craters of modern volcanoes.

The largest volcanic mountain on the southern limb of the moon, (called by some astronomers Tycho, and by others Mount Sinai,) like the largest volcanic mountain on the earth, Chimborazo, and like Mont d'Or and the Puy de Dome in Auvergne, has no deep crater on its summit. There are, indeed, the outlines of the crater, but it is nearly filled up; while, from the foot of this lunar mountain, diverging streams of lava flow in different directions, to the distance of six hundred miles. The largest currents of lava, from lofty volcanoes on

France, November, 1831. The opening of the cavern is situated on the steep declivity of a rock of magnesian limestone, subordinate to lias; it is about 27 feet in height, and 13 feet in breadth. The floor of the cavern, at some distance from the entrance, rises so rapidly to the roof, that it is difficult to stand upon it. The soil is composed of dolomitic sand, more or less intermixed with a greasy mud, and covered, in some parts, with stalagmite. About 170 feet from the entrance, on the lower part of the ascending floor, under a bed of sandy mud from eight to sixteen inches thick, human bones are found in abundance they are very fragile and light, and intermixed with fragments of pottery. The grotto divides into several low tunnels (boyaux.) M. Tessier crawled along some of these descending tunnels, and found numerous bones of bears intermixed with those of men and infants, among dolomitic sand. But the most remarkable circumstance he mentions is, that bones of bears are incrusted with mud, and attached to the roof of the cavern. This proves that the cavern had been filled with bone mud (limon à ossemens) by the violent action of water, otherwise the bones of bears that inhabited the cavern would all have been found at the bottom. It is most probable that the cavern was originally inhabited by bears, and afterwards inundated by mud and water; that, at a later epoch, it became the residence or sepulchre of a rude people; but was subjected to a second inundation, which drifted the bones of bears and men into the distant low passages. At a still later period, the cavern had been occasionally used for a sepulchre by the Romans, as a skeleton, with a lamp and bracelets, were discovered on the surface of the floor. M. Tessier says, that the river Gardon, before it had excavated its present deep bed, might have occasionally caused great inundations, which filled the cavern with water. Whatever theory may be adopted respecting the former inhabitants of the cavern of Miallet, the bones attached to the roof prove the agency of water, and sufficiently explain the cause by which the remains of bears and men may have been intermixed.

hornblende, with grains of quartz. In this rock are numerous globules composed of concentric coats of hornblende and felspar, varying in diameter from one inch to three or four inches. In the centre of each globule there is a particle of hornblende. The globules appear intimately united with the rock in which they are imbedded, and cannot be detached from it. The orbicular granite takes a more even polish than the porphyry, and is one of the most beautiful granitic rocks.

ON FRESHWATER FORMATIONS.

DR. MACCULLOCH has claimed the merit of being the first writer who directed the attention of geologists to the circumstance, that some species of marine animals can live when removed into fresh water. But, in the second edition of this work, published in 1815 (p. 461 and 462), I stated my opinion that the evidence of certain species of shells being marine, or freshwater, rested on too slight a foundation; and that I was informed by Mr. Leckie of a circumstance which proved that marine animals have greater facilities of adaptation than naturalists generally suppose.

"The lake of Lentini in Sicily is stocked with a sea fish called the Cefalo-a species of mullet caught in the Mediterranean, and thrown into the fresh water of the lake, where they not only live, but increase greatly in size and improve in flavour, and are a considerable article of luxury in the island. This lake has no communication with the sea, and is chiefly filled with rain water."

The evidence of certain geological formations being marine or freshwater, cannot rest securely upon the occurrence of a few species of marine or freshwater shells, but on the general character of the assemblage of organic remains. If shells belonging to species or genera that are known at present as inhabitants of rivers or lakes, occur with abundant remains of terrestrial animals and vegetables in particular strata, and no marine species are mixed with them, we can have little doubt that such strata were deposited in fresh water: nor would the freshwater origin of the strata be invalidated by the admixture of a few individuals of marine species; because we might with probability infer, either that the animals were capable of living in fresh water, or that they had been drifted by high tides or inundations. The character of the formation must be taken, as before mentioned, from that of the assemblage of organic remains.

FURTHER OBSERVATIONS ON THE INTERMIXTURE OF HUMAN BONES WITH THOSE OF BEARS, IN THE CAVERN OF MIALLET.

The remarkable intermixture of human bones with those of bears, in the cavern of Miallet, in the department of Gard (see p. 307.,) has received further elucidation by a subsequent examination of M. Tessier, of which an account was read to the Geological Society of

France, November, 1831. The opening of the cavern is situated on the steep declivity of a rock of magnesian limestone, subordinate to lias; it is about 27 feet in height, and 13 feet in breadth. The floor of the cavern, at some distance from the entrance, rises so rapidly to the roof, that it is difficult to stand upon it. The soil is composed of dolomitic sand, more or less intermixed with a greasy mud, and covered, in some parts, with stalagmite. About 170 feet from the entrance, on the lower part of the ascending floor, under a bed of sandy mud from eight to sixteen inches thick, human bones are found in abundance: they are very fragile and light, and intermixed with fragments of pottery. The grotto divides into several low tunnels (boyaux.) M. Tessier crawled along some of these descending tunnels, and found numerous bones of bears intermixed with those of men and infants, among dolomitic sand. But the most remarkable circumstance he mentions is, that bones of bears are incrusted with mud, and attached to the roof of the cavern. This proves that the cavern had been filled with bone mud (limon à ossemens) by the violent action of water, otherwise the bones of bears that inhabited the cavern would all have been found at the bottom. It is most probable that the cavern was originally inhabited by bears, and afterwards inundated by mud and water; that, at a later epoch, it became the residence or sepulchre of a rude people; but was subjected to a second inundation, which drifted the bones of bears and men into the distant low passages. At a still later period, the cavern had been occasionally used for a sepulchre by the Romans, as a skeleton, with a lamp and bracelets, were discovered on the surface of the floor. M. Tessier says, that the river Gardon, before it had excavated its present deep bed, might have occasionally caused great inundations, which filled the cavern with water. Whatever theory may be adopted respecting the former inhabitants of the cavern of Miallet, the bones attached to the roof prove the agency of water, and sufficiently explain the cause by which the remains of bears and men may have been intermixed.

in other fields. Still, when we remember that geology, as a regular science, is, in every country of Europe, of recent origin; and that, in the United States, most of its early cultivators are still on the stage, we have great reason to take courage and work on.

On the present occasion, we will annex some remarks on the nature of geological evidence, and its consistency with sacred history, making use of some portions of the "Outline."

Statement of the subject.

By some, this discussion may perhaps be now regarded as obsolete. In the minds of well instructed geologists, this is probably, to a great extent, true. Still, the Vindicia Geologica and the Reliquia Diluvianæ of Professor Buckland, the Preliminary Discourse to Mantell's first volume on the Geology of Sussex, that of Phillips in his Geology of Yorkshire, that of Conybeare and Phillips in their Outline of the Geology of England and Wales, some of the lectures of Cuvier, and, of late, the Geology of Dr. Ure, the Mosaic and Mineral Geology of Penn and of Higgins, besides the distinct work of Chaubard, "Offrant la concordance des faits historiques avec les faits geologiques," and various others of earlier date, sufficiently prove, that the subject is not quite at rest in Europe.

In this country, the cultivation of scientific geology is of so recent a date, that many of our most intelligent and well educated people are strangers even to its elements; are unacquainted with its amazing store of facts, and are startled, when any other geological epochs are spoken of than the creation and the deluge, recorded in the pentateuch. But, it is beyond a doubt, that there are innumerable and decisive proofs of successive revolutions, and of a gradual progress in the course of geological events, implying, on the whole, a regular order in the formation of the crust of the planet, interrupted by occasional disorder and convulsion. These events necessarily imply much time, and cannot be referred, exclusively, to any course of diluvial action. It is impossible, for instance, upon any sound principles of philosophical reasoning, to refer to this cause, the extensive, various and interesting class of facts, relating chiefly to the consolidated rocks composed of water-worn ruins and fragments, and to those containing organized remains, in a mineralized state, entombed in the firm strata and mountains. This is a vast field of observation and instruction, and it is less known, even to the greater number of intellectual persons, than almost any department of knowledge. None but geologists study it with diligence, and none who have not made themselves