allow freedom of action in attending either Section, which was unanimously 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.

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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;

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

of all agents in terrestrial degradation, and by the mechanical action and transporting power of its waves, the materials of its shores are brought under the local influences of the shifting streams of tidal current, and are arranged in bars, island-beaches, and salient points or shoals, which have often a progressive increase on one hand, while undergoing degradation and removal on the other. These effects, as seen at Cape Cod, Block Island, Fire Island, Sandy Hook, Hatteras, &c., may be traced along our whole coast, from Massachusetts Bay to Mexico.

Such were the general views he had been led to entertain, on a subject which hitherto had received but little of that attention to which it was justly entitled; and he trusted that the inquiry now so happily commenced would be unremittingly pursued, under the favourable circumstances and auspices which were afforded by the general survey of the coast now in progress.

Dr. GOULD, in allusion to a statement, that substances are found drifted in opposition to the course of the wind, mentioned a fact, well known to persons resident on the coast, that when the wind blows off the coast, the waves throw up shells in greater abundance than when it blows in the opposite direction.

Prof. AGASSIZ adverted to the necessity of comparing the results of all observers, in order to arrive at important data for the guidance of geologists.

Prof. PEIRCE gave an account of the views of E. DESOR, Esq., "On the Local Distribution of Marine Animals," an abstract of which has not been handed in for publication.

Prof. AGASSIZ now interested the Section with his observations

ON THE FISHES OF LAKE SUPERIOR.

Prof. A. remarked that it had been his good fortune, the past summer, to have opportunities, in company with several friends, some of whom he now saw before him, to explore the northern lakes, and more especially Lake Superior. His attention had been called particularly to the fishes-a subject which has possessed for him, for many years, very great interest. His object was not so much to draw a comparison between the fishes of the United States and those of Canada, as to ascertain their geological distribution, and to satisfy himself whether they were indiscriminately distributed through all these lakes, or whether there were differences in their identity. Upon

carefully comparing them, he had found that they were entirely different that there are particular families in some of these lakes, and other families in others, and that they never leave their peculiar localities. There are families in Lake Huron, which cannot be found in Lake Superior, and that those in the latter do not move down to the lower lakes. He is satisfied that these fish originate in the localities in which they are found. It is a singular fact, he remarked, that these families are found in the same relative positions with the fish in lakes of Northern Europe, yet, although they agree, generally, with the European species, in their zoological classification, they are entirely different in structure and variety. The salt waters of Europe contain fish which the salt waters do not contain here; and among the fresh waters, although they generally agree, none are entirely alike-showing that there can be no transportation of the different varieties from one country to another, as it would be contrary to the laws of nature.

There is no convenience for the fish of our lakes to travel into the lakes of Northern Europe; and he proceeded to inquire whether these inconveniences were trifling or serious in their character. The subject, however, was too complex to arrive at a definite conclusion. In Lake Huron there are a great variety of fishes, belonging to the Perch family, which he classified under appropriate heads. It is well known, from geographical data, that North America is the oldest continental land known upon earth; and the general ancient character of this country is deeply impressed upon the mind of the geologist. He could not avoid the influence of this feeling when exploring the northern shore of Lake Superior. Is it not remarkable, he asked, that animals now exist, which are "old-fashioned" in their external zoological character, of the same type with those of the antediluvian periods? North America is the only place where the Garpikes live, and the Garpike is the only representative of the period when that fish alone existed!

Among the fishes there are two types-one with smooth, the other serrated scales. Those with serrated scales have usually two dorsal fins, but he had found in Lake Superior a new fish, with spines upon the opercular bones; and all the scales are hard and serrated. What has never before been observed in hard scale fishes, this species has, like the Salmon, an adipose, or fatty fin. Here, then, in Lake Superior, we have this old-fashioned fish, upon this old soil! He considered it important to trace our living animals in their relation to the fossils, as also that their geographical distribution should be noticed.