this very same subject, which he had brought before them from time to time, many years before the investigations now referred to were undertaken." He also added, "That he believed that geological science was on the eve of a great revolution.”— In the anniversary Address of Mr. Hamilton, President of the Geological Society last year, he made the following observations:

"Recent investigations have upset the ancient theories. It was formerly supposed that the crystalline rocks, particularly granite, owed their origin to igneous action. Now, it is well known that these granites are chiefly arranged in layers. The granite passes into gneiss, and the gneiss into mica schist and tale schist, and this is again closely connected with the green and grey slates; and it is well known that many of these rocks, formerly considered as plutonic, are really metamorphosed rocks."

These remarks refer principally to the order of the structure, and notice that granite is divided into bands, and changes into the slaty structure, as was described in my sections, and explained in my papers written in 1837 and since.

I shall now quote Mr. Hamilton's observations, in his last annual Address, with reference to the igneous theory; which I had opposed for so many years, and which at length is being given up as untenable :

"Another point," observed Mr. Hamilton, "to which I would invite attention is one of greater difficulty; it requires the serious aid of chemistry, mineralogy, and the laws of physical forces. The study of the older crystalline and metamorphic rocks has of late years greatly occupied the attention of many of those geologists who have examined the chemical and mineralogical conditions of formations. We are told that heat alone could not have produced the results we see; that water was an essential element in all these metamorphic operations; and we find, in the works of Sterry Hunt, Daubrée, Evan Hopkins, Delesse, Desor, and others, that even a high temperature was not necessary to produce these changes. Many of those results which have hitherto been considered as the effect of igneous action, are now believed to be owing to chemical action. It therefore appears that the time is come when it is desirable to investigate this question,-whether the theory of central incandescent heat is tenable? Whether the plastic conditions of the earth, to which its oblate spheroidal form has been attributed, be not owing to an aqueous rather than to an igneous origin? Water is an essential element in every rock, not only mechanically but chemically; and without attempting to revive the doctrine of Werner, it may be questioned whether we have not sometimes been disposed to overlook the importance of the part it has played in the construction and solidification of our earth.”*

* Quart. Journal of Geo. Society. May, 1866. Vol. xxii.

Mr. Hamilton, in making these observations on the influence of water in the formation of rocks, appears to have been under the impression that it was reviving the doctrine of Werner. This is a misconception of the modus operandi of the semi-aqueous action in the subterranean base, and shows that geologists, with all the advantages of modern discoveries and experiments in hydrothermal action, have not yet been able to comprehend the subject in its true light. The chemical or electro-magnetic wet process of crystallization, the production of metals from solutions, and the aggregation of crystals into large and compact massive rocks, must not be confounded with the old, crude mechanical theory, called the "Aqueous," introduced by Werner. It is as different from that, as the formation of a crystal is from that of a brick or a sediment. The one operates by attraction and chemical action, and the other by mere mechanical deposition or precipitation. The former action produces the crystalline rocks, and causes their upward crystalline growth, and the latter produces the superincumbent beds of deposits from substances held in suspension, and carried to lower levels by water.

THE FORMATION OF CORALS.

Before I went to South America, I had been taught to believe that corals were built by marine animalculæ, in a way somewhat similar to the formation of the honeycomb by bees.

I have had the opportunity of studying the growth of corals, in great variety and magnitude, on the shores of South America, the coast of the Isthmus of Panama, in some of the islands of the Pacific, in the Red Sea, at Singapore, Ceylon, in the coral islands of the Indian Sea, and on the coast of Australia, but I never detected a single case of a coral being built by animalculæ. I have seen, as it were, plantations of corals, cultivated for lime. I have seen their stems transplanted, and have watched their growth, both the mushroom and the arborescent form. The former appears to grow in the water like a fungus or sponge, and the latter has a growth and development like arborescent crystals, such as aragonite, &c. In fact, corals are not built up by insects, but are formed and grow like vegetation, having a beautiful internal structure, like the fibres, rings, and medullary rays of the trunks of coniferæ, &c. There are siliceous as well as calcareous plants found growing in the sea, but I shall not on this occasion. dwell longer on these formations. My object in thus noticing

the coral growth is to show how much we have yet to learn with respect to the formations and the productions of the earth.

THE GRADUAL FORMATION OF ISLANDS AND CONTINENTS.

We have abundant evidence that the continents were not suddenly formed in their present shape: they gradually acquired it by progressive enlargement of the crystalline growth, and successive elevations and depressions.

Australia presents a good example of this terrestrial action. The wharfs at Melbourne have risen six feet above the level of the sea during the last twenty years; i. e., a rise at the rate of four inches per annum. The coast of Lacepede Bay has upheaved eighteen feet in the last sixty years. This slow rate of upheaval, if it has continued during the last five hundred years, would be sufficient to raise two-thirds of Australia above the level of the sea. Indeed, a large portion of the interior of that country is still covered with lagoons of brackish water, and the whole of the low lands are strewed over with marine shells, similar to those seen on the bordering coast.

The upheaval is by no means uniform. In Western Australia it is less than in the south-east, and in some parts on the north the land is subsiding. The flat country in Western Australia is strewed over with beds of oysters and cockle-shells, of the species still existing in the adjacent seas, and these are found in various terraces, from two to twenty feet above the level of high-water mark. The remains of a vessel of considerable tonnage have been discovered in a shallow estuary near Vasse Inlet, which is now shut out from the sea. New Zealand, like Australia, is likewise more or less covered by comparatively recent beds of sands and gravel, containing marine shells similar to those now existing in the adjacent sea, occasionally mixed with the remains of terrestrial animals which have only recently become extinct, some of them having been seen alive in the last century.

The elevation of Tasmania is comparatively of a recent date. A great portion of what now constitutes the site of Hobart Town had been under water at a not very remote period. This is proved by the extensive deposits of comminuted shells, all of recent species, which are met with, for miles, along the banks of the Derwent. Some of these deposits are at an elevation of upwards of one hundred feet above highwater mark, and from fifty to one hundred yards from the water's edge, plainly showing thereby that a very recent elevation of the land has taken place. Judging from the condi

tion and comparative freshness of the shells and corals, the emergence of Tasmania from the sea could not be assigned to many centuries. Indeed, the general aspect of the southern part of Australia indicates comparatively modern upheaval, at first rapidly and then somewhat slowly, but, probably, subject to periodical increased intensity in the subterranean forces, as observed on the coast of Chili.

In the Bay of Panama, along the banks of the river Bayano, I have seen several terraces of marine beds, from the coast to about fifty feet above high-water mark, of comparatively recent origin. Since the town was built the upheaval has been sufficient to render the port worthless excepting for small boats and canoes. Hence the subterranean action is never at rest, and is constantly, although imperceptibly, rising or depressing the surface of the earth. The fundamental base of the dry land is composed of an aggregation of crystals, formed into masses of rocks of various degrees of compactness, from mere pasty consistency to the hardness of quartz, presenting various structures, from the compact granular to the laminated formations known by the names of granites, porphyries, gneiss, and schistose rocks.

The predominating crystals of which the fundamental base, or the primary rock, is composed, are quartz, felspar, mica, talc, hornblende, chlorite, schorl, carbonate of lime, sulphate of lime, fluor spar, &c., &c. Besides these conspicuous crystals there are also disseminated in the primary rocks, either in minute grains or in solution, all the known metals; and these are often seen gradually developed by crystallization from their solvents in subterranean vacuities, caverns, mineral veins, &c., and the aggregated crystalline compound becomes active en masse.

The crystals of which the primary rocks are composed could never be the production of incandescent matter, as they all require a certain proportion of water in combination for their formation, to which their transparency is in many instances referable.

Thus, crystals of sulphate of lime are of a glossy transparency, and of regular figure: this is due to water; heat them and they crumble into a white powder. Quartz contains from 5 to 20 per cent. of water; felspar from 3 to 10 per cent.; and many compounds as high as 45 per cent. of water. All the rocks, the most solid and compact, lose a large proportion of their weight on being exposed to the sun, and many decrepitate when exposed to strong heat: the weight thus lost being water. Indeed, there is scarcely a substance known but what is either found in solution, or may be dissolved in an

aqueous compound. The apparent insolubility of quartz was at one time the argument held in favour of the igneous theory, although silica was found in solution. Silica is now artificially dissolved, and can be obtained as plastic as clay; therefore there is not a single case connected with the materials of which the globe is composed to warrant the assumption that they originated from fire. On the contrary, all the observed facts confirm the belief that the crystals first came forth and grew from water, and that the lands have gradually risen from the deep.

The evidence of successive elevations and depressions is so manifest as not to require further remarks. The evidence is cqually strong that the various deposits of organic remains have not only been lifted from the deep, but have also been carried en masse from clime to clime at a slow rate, inasmuch as the deposits of the northern hemisphere, as far as the Arctic region, contain all the organic productions of the world. This subject, however, will have to be treated separately, in connection with the probable ages of geological formations founded on astronomical data.

SUPERFICIAL CHANGES.

The changes going on over the face of the earth are much more rapid than the public at large appear to be aware of. The deposits in deltas are frequently formed in great thickness, in a comparatively short time, by mountain torrents, floods and avalanches. The great region between the rivers Orinoco and the Amazon is intersected by rivers, and covered here and there with shallow lagoons, subject to periodical floods. This country is so overloaded with thick and gigantic vegetation as to render it impenetrable to bulky animals. In these regions man is considered as a being not congenial to such a state of nature. The earth there luxuriates in its gigantic palms, fern-trees, club-mosses, and various rank and succulent plants. The crocodiles, sharks, iguanoes, &c., are masters of the rivers; and the jaguar, pecari, tapir, boa, and a variety of reptiles, rove and infest the banks, and the high grass surrounding the lagoons, nothing impeding their increase; and are almost the sole possessors of the country-as in the imagined primæval world-without fear and without danger of being disturbed by any human being. Were this region to sink 320 feet, the whole surface would be covered by the Atlantic ocean, and the eastern declivity of the Andes would become again what it was before, a shore of the ocean. In many parts of the country are large plains partially covered with gravel,