those observed on this clay bed exactly resemble each other in form and size.

It may be added that we have found at this locality large surfaces covered with scratches similar to the striæ made upon stone by drift. Hence we infer that the latter may sometimes have been made in a similar way. In the spring, the Connecticut river is swollen to an unusual size, and filled with masses of ice and floatwood. Driven by the current, they are forced over this bed while it is scarcely covered by the water. And thus the surface becomes covered with striæ: all pointing in the same direction except a few which cross the others at a small angle.

The phenomena of mud-veins are also illustrated by a fact noticed at this clay bed. Great heat causes clay to contract, as may be seen in deposits left by small pools of muddy water, which have been exposed to the sun. The surface of this bed in Hadley is similarly divided during seasons of drought. So when in Triassic times a clayey mud was cleft in this way, the returning tide, or a storm of rain would fill the fissures with detritus, producing the mud-veins which are very common in the rocks of the Connecticut valley. Another fact may be mentioned here. The summers during which the best specimens of these alluvial foot-marks were obtained, were quite dry. If a long drought succeeded a copious shower, a fine crop of tracks was gathered. Hence it may be inferred, that when the Triassic ichnolites were made, the climate was tropical. This will explain the remarkably fine preservation of delicate ichnolites.

This locality serves to explain why among so many fossil footmarks as have been disinterred, scarcely a relic of the animals themselves have been found. For three years I have not noticed on this clay bed any other trace of the animals besides their tracks.

As this seems to be the common feeding-ground for many species, if any of them died there, their remains would probably have been devoured or floated away by the water. Such a spot therefore, is the least likely of any to contain organic remains. As it seems to be a type of the spots where fossil footmarks occur, we may reasonably infer that the paucity of such remains in the Triassic rocks is not strange.

ART. XL.-Emmons on American Geology.*†

THE laborious investigators of our American geology can scarcely find time for the preparation of popular treatises, which shall embody the results of their researches, and the consequence too often is that this labor is left for those who are most unfit for the task. It is but a few months since another pen than ours called attention to Mr. Marcou's poor caricature of a geological map of North America, and showed that both the map and the accompanying text are full of errors and mis-statements, calculated to give foreign readers most erroneous ideas, not only of the state of American science, but of the true geological structure of the country. We recall this with more regret, because we observe that Sir R. I. Murchison was deceived by Mr. Marcou's pretensions, and lent to the map a certain sanction in the pages of Siluria, before he was apprized of its worthlessness. The fact that Mr. Marcou is a comparative stranger in our country may explain his ignorance though not his presumption; but we regret to say that no such excuse can be urged in behalf of the author whose name appears at the head of this article. Dr. Ebenezer Emmons is known to the American public as having been the geologist charged with the examination of the northern district of the State of New York, and as the author of the so-called Taconic System; besides which, as geologist to the State of North Carolina, he has given us two or three reports, which we may notice further on. With these antecedents, he presents to the world the first part of a work on American Geology.

The author seems to have sat down to his task without any well defined plan, and hence the promiscuous arrangement, repetitions, obscurities, and contradictions of the volume. As to scientific accuracy, style, or even English grammar, the work is filled with errors. He objects in his preface to the works of American geologists, that they are not American, and proposes to give us a truly American geology. Our readers shall judge how far his work is worthy of such an honorable title.

Passing over his preliminary remarks for the present, let us glance at our author's classification of rocks. Besides the Hydroplastic rocks embracing all the sedimentary deposits, and the Pyroplastic, including all traps, lavas, etc., we have a third class, Pyrocrystalline rocks, divided into laminated and massive, this last embracing "granite, syenite, hypersthene rock, serpentine,

* American Geology, containing a statement of the Principles of the Science, with full Illustrations of the characteristic American Fossils; to be completed in four parts, with an Atlas and a Geological map of the U. States; by Ebenezer Emmons. Part I. Albany, 1854.

The Editors make no apology for inserting a review of another of Dr. Emmons's works, other than the fact of its recent publication and its especial claim to notice.

rensselaerite, and octahedal iron ore," besides what he calls pyrocrystalline limestone, as distinguished from laminated limestone, which he however places in the laminated division of his pyrocrystalline rocks, with laminated serpentine, gneiss, mica slate, hornblende, talcose slate, etc., p. 43. He here objects to the name of metamorphic rocks as applied to gneiss, and the subsequently named rocks because "its use is theoretical, and was thus applied on the hypothesis that those rocks are altered sediments, of which there is no evidence." The italics are our own, but we shall let the author explain his notions of the origin of these pyrocrystalline rocks, which he tells us have been produced by the consolidation of the earth's crust.

"A pellicle must have ultimately been formed, and which still maintains its existence as a constituent part of it. From the manner in which the surface cools, the consolidated masses which successively form, must lie in contact with the inferior surface of the first-formed pellicle. The thickness of the crust increases from below."

So that the order which is observed in the hydroplastic rocks is inverted, and "the newer are beneath and the older above."-p. 45.

On the next page we are told that the first formed rocks are the most highly crystalline, because the heat of the earth was greatest at the epoch of their formation. We are at a loss to conceive what greater heat than that of a central fused mass can be required, or what better condition for crystallization can be conceived than that of a mass slowly congealing between the outer crust and the central fire. We are then told that granites are the first products resulting from the cooling of the earth's crust; as a consequence of the inverted order of succession already described, it would follow according to our author that granites should overlie all the other pyrocrystalline rocks, which we should find beneath it, arranged in consecutive layers, the least crystalline ones, like talcose slates, serpentines, lowest down! He further adds, "traps, and greenstones, never form those parts of the earth's crust which belong to the most ancient periodsthe rocks of the most ancient periods being represented by granites and gneiss, whose structures are eminently crystalline."

The author, while he finds it difficult in speaking of veins and dykes of granite, (whose subsequent intrusion he admits,) to distinguish this rock from his pyroplastic group, is not less disposed in the next paragraph to class greenstone with granite as a pyrocrystalline rock. Further on, serpentine, whose pyrocrystalline nature he has already asserted, is spoken of as an igneous rock, which, like other rocks of this class, has been formed at different periods. Quartz rocks, even when they have the character of sandstones, are set down as pyrocrystalline when found in the company of talc and mica slates, while of clay slate, which is described as a pyrocrystalline rock, he says, "I should not regard

it as an eruptive rock, and place it in this connection, were it not generally placed among the primary rocks, and were it not also quite common in proximity with veins in granite in North Carolina and other places."-p. 104. Good and sufficient reasons truly. Elsewhere we read of pyrogenic rocks, that "at one extreme of time the rocks formed were all crystallized, while at the other they all want it."-p. 62. There are no good grounds for distinguishing a third class of rocks distinct from those designated by Mr. Emmons as hydroplastic and pyroplastic. The former may be so far altered as to become crystalline, and even undergo fusion, so as to take the shape and position of pyroplastic rocks; indeed it would be difficult to prove that any of these latter rocks have any other origin than the fusion of subjacent hydroplastic strata. The pyrocrystalline limestones are introduced to our notice by Mr. Emmons in the following language, literatim :

"The class of limestones under consideration, though they contain many minerals, yet as a rock it is not associated with any important ones except serpentine, and its congener rensselaerite. * *The circumstances under which this rock occurs in this country, warrants its recognition as a rock quite as distinct from all others as granite. It is by no means a metamorphic mass."—p. 57.

Having mentioned the limestones of Northern New York, and those of the southern counties of the same State, he proceeds to object to the view that they are Silurian strata altered by heat. In order to sustain his own notion of the igneous origin of crystalline limestones, Mr. Emmons confounds, perhaps ignorantly, the limestones of two different regions occurring under very unlike conditions. Those of Southern New York and the adjacent parts of New Jersey and Pennsylvania have been clearly shown by Rogers and by Mather to be of Silurian age, while the crystalline limestones of Northern New York belong to a formation older than the Potsdam sandstone. Mr. Hunt, of the Geological Survey of Canada, in a paper on the crystalline limestones of Canada and the Northern States, read before the American Association at Washington, in May last, and published in this Journal for September, has clearly pointed out the facts in these two cases, and has shown that the different limestones cannot for a moment be confounded; and that they have nothing in common, but the crystalline minerals which belong to the altered limestones of all geological ages. In Northern New York, as Mr. Hunt has shown, the presence of great stratified masses of a lime feldspar rock, having generally the composition of andesine or labradorite, and often mixed with hypersthene, characterizes the group to which the crystalline limestones belong, while there is nothing to represent these among the altered Trenton limestones of Southern New York.

Mr. Emmons brings forward many cases in illustration of his theory of the hypogene origin of these crystalline limestones, such as their occurrence in veins and intruded masses among the feldspathic and quartzose rocks of the region. That such cases exist is very true; but any one who has intelligently studied them, will admit that the limestones are nevertheless interstratified with these felspathic and quartzose rocks, and that they may be traced for miles in the direction of the undulations, maintaining throughout, the same relation to the accompanying strata. We speak from personal observation. This is indeed so evident, that Mr. Emmons both in his Geological Report, and in the present work, finds no other means of describing the distribution of these limestones in New York, than to speak of them as beds, running N. E. and S. W. At the same time, Mr. Hunt, in the paper already referred to, observes that the limestone appears at some period to have been rendered almost liquid, and to have been subjected at the same time to great pressure, so that in many cases, it has flowed around and among the broken and often distorted fragments of the accompanying silicious strata, as if it had been an injected hypogene rock." (This Journal, [2], xviii, p. 194.)

The crystalline limestones of Pennsylvania, Virginia, and North Carolina are described by our author as "ranges belonging to the laminated and schistose rocks," yet he says, all these limestones must be regarded as belonging to the eruptive class, p. 83. According to him they resemble the limestones of the Hoosick range in Western Massachusetts, which are also pyrocrystalline, and are not to be confounded with the Vermont and Berkshire marbles, "which are of sedimentary origin and belong to the Taconic system." He then tells us that these two limestones are related to each other as granite and gneiss, as if he admitted the sedimentary origin of gneiss, which he has already classed with granite as pyrocrystalline. The distinction which he draws between the Washington and Pittsfield marbles is as baseless as the Taconic system to which he refers the latter. Both of these limestones belong to a single formation which may be traced with a continuous outcrop, from the exposures holding Trenton fossils near Missisquoi Bay, in Canada, through the marbles of Rutland, of Berkshire and of Westchester Co., N. Y., the alteration gradually increasing, until we reach Orange Co., New York, and Sussex Co., N. Jersey. Yet the sedimentary origin of these rocks is not more clearly marked, than is that of those of the Laurentian series, which, having been disturbed and rendered crystalline, are, along their whole outcrop in Canada and New York, covered by the unaltered and horizontal paleozoic strata of the New York system, the base of which is sometimes a conglomerate of these crystalline rocks. In the face of these facts Mr. Emmons would have us understand that the eruption of the crystalline limestones