allow freedom of action in attending either Section, which was una. nimously agreed to.

The Chairman reported the recommendation of the Standing Committee, as to the order of business for the day, which was adopted, and the Section proceeded to take up the first paper submitted, which was upon

THE THEORY OF THE GEOLOGICAL ACTION OF THE TIDES. BY LIEUT. C. H. DAVIS, U. S. N.

It was presented and read by Prof. PEIRCE, of Cambridge University, who prefaced it by a few remarks on the general principles of the theory, the object of the paper being to exhibit the action of the moon, as tending to alter the figure of the earth.

By a study of the tidal currents on the north-eastern coast of the United States, Lieut. Davis has been led to the discovery of a connexion between the ocean tides and currents, and the alluvial deposits on its borders and in its depths. The connexion is thus traced:-the direction and velocity of the tides at any place where these deposits exist, that is where the ocean is freighted with matter held in suspension, decides the form, amount and locality of the deposits. The direction of the tides is different at different places, but the result of their action is to produce certain uniform or similar formations; and it was the observation of this which led Lieut. Davis to the introduction of a tidal theory into Geology, the object of which is to develop the laws by which aqueous deposits (of the sea), made during periods of quiet action, have been regulated, and to show that such laws must always have operated, except when suspended or controlled by the violent changes that mark certain geological epochs. Lieut. Davis applies these principles of tidal action, to explain the cause of those great sandy deposits on the north-eastern borders of this continent, as well as those at the bottom of the Bay of Biscay (the Landes of France), and in the North Sea (Holland, &c.).

Following in the steps of that theory, which aims at accounting for the changes of previous ages by causes now in operation, and recognising the controlling influence of the ocean in producing some of these changes, Lieut. Davis calls the attention of geologists to the fact, that the ocean has been subject to dynamical laws as permanent as its existence, and in their action no less regular than permanent. He traces the results of these laws first in the local features of the New England coast, where they are exemplified upon a small scale;

lowed, as in Goldfuss' work, by other remarks corresponding to those in German.

The fossils described having chiefly been found in the vicinity of Dayton, some notice of the various formations in which they occur may be proper. They consist of five successive calcareous deposits, which are exposed at various places within a distance of three miles from the town, all differing very much from each other, in general appearance, texture, colour, and in the fossils which they contain. The lowest, universally called the "Blue Limestone," corresponding with the Lower Silurian, consists of innumerable layers, varying in thickness from less than a fourth of an inch to eight inches or more, with layers of marl of similar varying thickness intervening. It is the only rock which appears at the surface in the south-western corner of Ohio, and the adjoining parts of Indiana and Kentucky. It is principally made up of bivalve shells, but contains numerous corals and fragments of trilobites and orthoceratites. The corals are of the genera Astrea, Anlopora, Ceriopora, Cyathophyllum and Retepora; and none of the species found in this formation have ever yet been found in those above it. The same circumstance is believed to be true with regard to the species of shells. The colour of the fossils is the same as that of the stone in which they are imbedded.

Upon the Blue Limestone lies a bed of marl, varying in its thickness, at different points, from ten to sixty feet. It does not include any solid rock, either in layers or fragments; being of the same composition, texture and colour, from top to bottom, although its colour varies a little at different places, at some distance from each other. No fossils have been observed in it.

On this bed of marl rests a formation of limestone, usually between twenty and forty feet in thickness, composed of the remains of a great variety of animals, intermixed with semi-crystalline scales. Sometimes, fragments of encrinites constitute almost half the mass. The colour is variable; in some places nearly white, in others reddish, in others dusky brown; but it is most frequently of a wax yellow, and the formation is usually termed the "Yellow Limestone." The fossils found in it, besides the encrinital remains, are chiefly corals, with a very few shells and trilobites. The corals are generally in excellent preservation, differing very little, if at all, in colour and texture, from recent specimens. Their colour is of a bony whiteness, not being influenced by that of the rock in which they occur, whether white, red, brown or yellow. They are of the genera Astrea, Catenipora, Cellepora, Cyathophyllum, Eschara, Favosites,

Flustra, Gorgonia, Lithodendron and Retepora. Of these genera, none of the species found in this formation are seen in either of those above or below it, except the Catenipora, Eschara and Gorgonia. The Catenipora is found in the Quarry Limestone, and its impressions, and those of the Gorgonia and two species of Eschara, occur in the Silicious Limestone.

Upon the Yellow Limestone rests a formation, which is usually termed the "Quarry Limestone," as, on account of its superior quality, it is almost the only stone quarried in the vicinity for building purposes. It consists of several layers, easily separated from each other, making an aggregate thickness of about four feet, which it is. not known to exceed. It is of a light grey colour, and very hard and compact. The fossils which it contains differ but little in colour from the stone, and are so completely enveloped in it, that they are not easily found. The genera that have been observed are Astrea, Catenipora, Favosites, Sarcinula and Syringopora. The species are all peculiar to this formation, except those of the Catenipora, as mentioned before.

The Quarry Limestone is covered by a formation of "Silicious Limestone," in which the silicious matter, in fine grains, constitutes about fifteen per centum. The rock has the colour of ashes. It is

six or seven feet thick, near Dayton; but as it extends to the north and east, the thickness increases to fifty or sixty feet. It usually contains only the impressions of fossils, the whole substance of the shell or coral having, in most cases, disappeared. The corals, of which impressions are left, belong to the genera Catenipora, Coscinopora, Eschara and Gorgonia.

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To the last three formations, collectively, DR. LOCKE, in the Ohio Geological Reports, has applied the general designation, “ Cliff Limestone.' They do not pass imperceptibly into each other, by a gradual alteration of colour, texture and general appearance; but the change is immediate and total, the lines of separation being definitely marked; and the fossil characteristics, with the exceptions already mentioned, are also entirely different.

The gravel, in the beds and banks of the streams, and in the neighbouring hills, affords a great variety of fossils. Although the principal part of it is derived from the limestone of the vicinity, a very considerable portion of it is made up of pebbles which have a different origin. These consist of fragments of primary rocks, of all the various kinds seen in the boulders scattered over the country, and of numerous fossiliferous varieties of calcareous and silicious rocks, the

and afterwards applies his reasoning to those vast alluvial deposits, which form conspicuous features in the geography of the world.

Going behind the actual geological period, Lieut. Davis believes that he can discover satisfactory proofs in the geological maps of the United States, by Mr. Lyell, that the successive deposits of the cretaceous, tertiary, and post pliocene periods (including in this last the stratified drift only), have been made in obedience to the tidal laws. He hopes, by these laws, to explain the geological peculiarities of the great plains of North and South America, and the deserts of other countries. And reasoning back from a principle of conformation discoverable in the banks, shoals, hooks, bars, &c., &c., of the present time, he thinks it not improbable that the character of the tidal and other currents of the earlier ages may be developed.

Although Lieut. Davis has given to his views the name of a “Tidal Theory in Geology," yet he does not limit his inquiries to tide currents alone, but embraces in his theory all those oceanic currents which produce similar effects. Thus the sandy formations on the coast of the gulf of Mexico, and the geographical distribution of the coralline detritus in the China sea, and elsewhere, in connexion with the tides and currents of the particular region under notice, do not escape his attention.

Lieut. Davis announces as one of the discoveries resulting from his investigations, that there is an intimate relation between tides and deltas. River deltas are only formed where there is little or no tide. Where there is a tide of a positive and regular character and action, the conflict between tidal and river currents gives birth to estuaries, and it is expected that the limit of the bay form will be found to depend upon the limit of action of the tides.

Lieut. Davis is employed in preparing a paper, in which the dynamical action of the tides is explained, and the facts and observations upon which his theory is founded, are stated in detail. This paper will be accompanied with the necessary illustrations.

It would occupy too much space to enter here into these details. The attempt would leave them necessarily incomplete.

An interesting discussion ensued on Lieut. Davis' views, in which Prof. PEIRCE, W. C. REDFIELD, Esq., and Dr. A. A. GOULD, participated.

Mr. REDFIELD said he was gratified in finding this inquiry entered upon by the able officer connected with the Coast Survey. The subject had attracted his own attention at times, and particularly during a

visit to the low country and shores of North Carolina, in the vicinity of Cape Hatteras, in the year 1840; and he had derived many interesting facts relating to it, from the lake and coast surveys executed by the Government, apart from his own observations. It was his misfortune to have heard but a portion of the interesting essay of Lieut. DAVIS, and he feared he might be liable to a misapprehension of some of its bearings. For himself, he had been led to conclude, that the great shoals of Newfoundland, George's, Nantucket, and Lagullus, did not owe their origin to the general transporting power of the Gulf Stream, or the current of Lagullus, nor to the direct action of the great tidal wave, in its progress over the ocean. He thought that none of these could hold in suspension and carry over great distances the materials of these shoals, nor exert a moving force upon the ocean bottom which lies beneath their flow. Even if the latter could be true, the materials would undergo a rapid abrasion, from their rolling motion beneath the incumbent waters, and would soon be reduced to an impalpable condition, and scattered abroad over the ocean bed, forming a soft and oozy bottom, such as now results from other abrasions, or as once was the condition of our clay slates, and other analogous formations.

Mr. R. then proceeded to state facts illustrative of the rapid reduction, by abrasion, of the materials set in motion by currents—as on the Hudson river, where, near the city of Troy, the transported detritus of the river shores and bed, consisted of large gravel and worn pebbles, often of the size of the eggs of the goose or hen. Six miles lower, near Albany, the bottom was reduced to a fine gravel, of the size of the different varieties of beans and maize. Next, four or six miles below Albany, it was in the condition of a coarse or fine sand; and long before reaching Hudson, thirty miles from Albany, the channel bottom was found to be of soft materials, such as form the clay beds of the river shoals and flats; and we have no evidence that any sands or coarser materials can be found in the great channel bottom, from thence to the ocean at Sandy Hook, a distance of 130 miles. The bar and shoals near Sandy Hook, like those which obstruct the mouths of other rivers, were derived from the materials of the adjacent beaches, abraded and set in motion chiefly by the waves, and especially in storms, these effects being blended with the action of the local currents. Hence it results, that where the mouth of a river is protected from these effects by points or promontories of rock, we almost invariably find a free and open channel.

The ocean, as has justly been said by Mr. Lyell, was the greatest