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tant discoveries; and that, however little value, in the abstract, would attach to an enumeration and description of the shells, zoophytes, and other remains of our marl banks, they are absolutely essential in studying the physical history of this portion of the globe, and may prove of some assistance not only in guiding the researches of the farmer after marl, but in directing his choice of cal careous manure, when various deposites of this substance are offered for his selection. Of the latter point, several striking illustrations might be adduced-but I shall content myself, for the present, with the statement of a single fact. A small shell of rough exterior, and rather irregular form, a species of chama, is frequently found in very extensive beds in this vicinity and at other points, forming nearly the entire calcareous portion of the deposite. From its peculiar form and friable character, it is most generally in a condition to be eminently serviceable as a manure. As the strata both above and below are often of a very different texture, though perhaps nearly equal to it in regard to their calcareous contents, a choice is at once presented to the farmer, in which, he will be guided even more by the nature of the shell embedded, than by the comparative abundance of carbonate of lime. But so little attention has been paid to the characters of the fossils contained in our marl-banks, that even in places where the manure has been longest and most successfully in use, a less valuable stratum is sometimes selected in preference to one of superior fertilizing power. A more minute observation of such particulars, can scarcely be expected, in the absence of some popular guide, in the form of delineations and descriptions of the more prominent shells, exempted as much as possible from technical or merely scientific phraseology. Some such illustrations may hereafter be furnished in a cheap form in the progress of a geological examination of the eastern region of our state.

estates in this vicinity, are peculiarly rich in this ingredient, and are hence, as well as from their friable texture, generally selected in preference to all others. In some of these deposites, as large a proportion as thirty, and in some specimens forty per cent., has been found; and in cases like this, if we are to trust to the experience of New Jersey, a very marked addition to the fertilizing power of the marl must be ascribed to the presence of this ingredient.

In alluding thus to the influence of the green sand as an auxiliary manure, the inquiry naturally arises, to which of its ingredients are its meliorating effects to be ascribed, or do they arise from the conjoint action of the potash and oxide of iron which it contains? To this inquiry, perhaps, it would be premature to attempt to respond. At all events, the rationale of its action cannot be given with that certainty, which in such matters, it is desirable to attain. As stated in the former communication, its components are protoxide of iron, potash and silex; the latter ingredient appearing to act, as it is known to do in many rocks, in the capacity of an acid. In virtue of the potash contained in the green sand, we would naturally infer an agency in neutralizing acids, similar to that of lime, or its carbonate-and the extent to which the manure possesses this property, must appear still further increased when we advert to the chemical nature of the protoxide of iron.

Iron, like most other metallic bodies, combines with oxygen in more than one proportion. These compounds, or oxides as they are termed, are two in number, and in accordance with the general rule adopted by chemists in designating this class of substances, that which contains the least proportion of oxygen, is called the protoxide--that containing the most, the peroxide. The rust of iron, and the red coloring matter of ochreous clays, and of bricks and tiles, are impure specimens of the peroxide of iron. The protoxide is never found in Since the publication of my former paper, a an uncombined condition; and such is the avidity great number of additional observations have been with which it imbibes an additional quantity of made with regard to the green sand contained in oxygen, or unites with carbonic and other acids, our ordinary middle tertiary marl. Its uniform that it undergoes a rapid change whenever disenpresence in this deposite, in a greater or less pro- gaged. Hence, under favorable circumstances, portion, seems now to be sufficiently established. a strong neutralizing action might be anticipated That it is generally present insufficient quantity from this ingredient of the green sand. We may to enhance in any important degree the agricultu- therefore, for the present, rest our explanation of ral utility of the manure, it would be going much the agency of this manure upon the alkaline protoo far to assert; but that in many cases the propor-perties of these two constituents, the potash and tion is such as cannot fail of producing highly the protoxide of iron. But in suggesting this exbeneficial effects upon vegetation, would seem to planation, it must be freely confessed that, espebe demonstrated not only by the long experience cially as relates to the action of the protoxide of of the farmers of New Jersey with the green sand iron, it must be looked upon as problematical, itself, but by the observations of individuals and requiring for the establishment of its truth, an amongst ourselves who have been in the habit of experimental knowledge of the influence of this applying a calcareous marl in which this sub- substance upon the growing vegetable, of which stance is peculiarly abundant. In the vicinity of nothing has as yet been positively determined. Williamsburg, almost every variety of the com- As already indicated, when these inques mon marl may be found; but that which has been were entered upon, and at the time when my fire observed to produce the most striking effects as a communication appeared in the Register, he exmanure, has uniformly yielded to chemical exam-istence of a lower tertiary deposite in Virgi ination a comparatively large proportion of the had not been ascertained. The industry of Mr. green sand. When therefore, it is in the power Conrad had brought to light a formation of this of the farmer to make the selection, such marl nature in Alabama, and had led to the probatishould be chosen, as, along with a large proportion of calcareous matter in a suitable state of subdivision, contains also as great an amount as possible of this auxiliary manure. The beds of chama already referred to, as abounding on some

ference that it existed at Fort Washington in Varyland. Moreover one or two of the fossils ont nam ed from the editor of the Register encouraged the hope that it might be found in our own state. Th observations of that gentleman respecting the, "p

most recent systematic writer on geology, and one of the most learned and able geologists of the day, has distinguished four subordinate formations in the tertiary series-and has given to each a specific name, expressive of its relative period of deposition. Though unwilling to perplex the reader with the terms of science, I may perhaps be excused on this occasion for introducing the names here referred to, on the ground that they are likely to be met with frequently hereafter in geological descriptions of the tertiary deposites of this country-and as they are distinctive of things which are characteristically different, and which have received no other denominations so appropriate, they have a just claim to be received. The terms thus employed by Mr. Lyell, the distinguished geologist above alluded to, are

1st. Pliocene, indicating a majority of the contained fossils to be recent, and divided into newer and older Pliocene. Under this head are comprised some of the shell deposites near the mouths of our rivers.

seous earth of James River* had appeared some remarkable animal and vegetable forms being distime before, and though nothing positive could be tinct, while at the same time many of the species gained from them, in relation to the geological were observed to be identical with others now alive. character of the deposite, to which he affixed that The difference thus marked between the two sename, they threw out the important and saga-ries of deposites, uniformly prevailing wherever cious suggestion, that this earth was the same they were observed, led to the introduction of the with the green sand of New Jersey, or at least a term tertiary, to designate the upper and more resubstance of analogous character. We shall in cent. By scrutinizing in detail the tertiary series, the sequel, learn that though geologically the two it was soon discovered to consist of several disformations belong to periods which are distinct, tinct subordinate formations, characterized by pethe gypseous earth contains a large proportion of culiar fossils, and becoming more assimilated in that particular ingredient, (the green silicate of their organic contents to the existing living world, iron and potash,) of which the New Jersey de-in proportion as their position in the series apposite almost exclusively consists. We are there-proached nearer and nearer to the surface. The fore indebted to the editor of the Register, for the announcement of the important fact, that the green sand, or a substance analogous to it, existed in certain localities on the James River. Following up the suggestions of geological analogy, alluded to in my first paper, and stimulated by the observations and statements of Mr. Ruffin, I have been enabled by personal inspection, and through the kindness of correspondents, to ascertain with certainty, the existence of a lower tertiary deposite, throughout an extensive district of Eastern Virginia, and moreover to determine what is far more important to the agriculture of this region, that the deposite in question comprises immense strata of green sand, perhaps nearly equal in value to that which is in use in New Jersey. The reader, however, is by no means to infer from the existence of the green sand so abundantly, both in this lower tertiary and in the New Jersey formation, that the two deposites belong to the same geological era. I have already stated that the New Jersey green sand, is a secondary deposite-and of course anterior to the 2nd. Miocene, indicating a minority of the conformation here designated as lower tertiary. The tained fossils to be recent. To this formation beshells and other fossils, entombed in the two de-long most of our calcareous strata which have posites are strikingly different, and characteristic of previously been referred to under the title of middifference of geological antiquity. As it is desira-dle tertiary. ble that clear ideas should be entertained, in rela- 3rd. Eocene, signifying the dawn; indicating tion to the distinction here drawn, I would claim the presence of a few fossils analogous to living the indulgence of the reader, in presenting such species, or in other words a dawning of that condiexplanations, and illustrations, as are calculated tion of the animated world which now prevails. to throw light upon a subject in which, at least in Examples of this are furnished in the lower tersome particulars, all are obviously interested. tiary of Alabama, and the lower tertiary here alThe term primary having been adopted by geo-luded to as recently discovered in Virginia. logists as designating that extensive class of rocks The nature of the materials in which the fossils which from various indications, appeared in gene- of these different deposites are embedded is very ral to have originated first, and which are destitute various. Sometimes the formation is a soft sand of all traces of animal or vegetable existence- or clay-sometimes a sandstone or limestone of the title of secondary, was of course appropriated comparative hardness. In some cases the deposito a class, apparently of more recent origin, usu-tion appears, from the nature of the fossils, to have ally overlying the former, and in which, in many been made beneath the ocean-sometimes at the cases, an enormous accumulation of organic re- bottom of an extensive lake. In the vicinity of mains had been discovered. A minute examina- Paris, there are three marine formations altertion of these remains, consisting of shells, the nating with two of fresh water or lake origin; and bones of animals, &c., disclosed the curious fact from one of the latter, the celebrated gypsum or that they belonged to races of beings of which, at plaster of Paris is extensively quarried. In Virgipresent, there are only very few living represen- nia, no traces of a fresh water tertiary have as yet tatives. Subsequent observations, first systemati- been discerned. The general direction of the cally made by Cuvier and Brogniart in the vicini-deposite is horizontal, and the whole appears to ty of Paris, further demonstrated that overlying have been formed at successive eras beneath the e secondary formation of that region, there ex-waters of the ocean. isted an extensive series of deposites of great thickness, the fossil contents of which were, on the whole, very dissimilar from those of the former-not only all the species, but many of the most

cle on "Gypseous Earth," page 105.

From what has now been said, it will at once appear that strong features of resemblance are presented in the geology even of the more recent formations in this country and Europe. The most striking similarity exists between the secondary of New Jersey and that of many places in Europe

as far as fossil contents are concerned. But in Eu- or lower tertiary formation. Yet at some poir te a rope a great proportion of these fossils are embed- stratum of the ordinary middle tertiary marl reste ded in chalk; whereas, in New Jersey, no chalk almost immediately upon the former, and would has been discovered, and its place is occupied by not by an ordinary observer be recognized as s green sand, very similar to that, which, in the for- tinct. At Tarbay, where this succession of strate mer localities, alternates with the layers of chalk. was observed, a thin and scarcely distinct la The lower tertiary or eocene of Virginia is founder of small brownish red pebbles intervenes be in a band of variable, and as yet unascertained tween these two layers of shells, seeming 15 breadth, traversing the state nearly in a direction mark a comparatively violent action of the wit from north to south. It makes its appearance on ters in the interval of the two deposites. But both sides of the Potomac, in a line a little east of an examination of the shells, in these two configaFredericksburg. It then crosses the Rappahan- ous strata, affords abundant evidence of Pe nock_near Port Royal, the Pamunkey probably belonging to distinct geological epochs. In the near Piping Tree, and the James River at Coggin's upper stratum the large scallops, the common oys Point. With regard to its course further south, ter of our marl, and all the usual ingredients of though its existence is probable, additional data our middle tertiary or miocene formation, may be are required. recognised. In the lower bed few or none of them In general character, this formation may be thus exist, but certain characteristic shells belonging to described. At the base of the cliff or bank, there the eocene period are entombed. Similar fossils usually exists a stratum of what at first sight ap- appear below, in the green sand beneath the gyppears to be a blue or black clay, but which, on fur-seous earth; and here a great variety of beautiful ther examination, is found to consist principally of specimens may be discerned. An enumeration of particles of the silicate of iron and potash, which these fossils in this place would of course be atwhen dried, becomes of a lively green color. tended neither with utility nor interest, and inMingled with this substance are portions of com-deed, were it advisable in the present stage of the mon clay and sand, and numerous minute shining inquiry, it could not be made, on account of the scales of mica. Embedded in the mass, and usu- necessity of comparing the specimens with shells ally in a very friable condition, numerous shells from other localities in Europe and this country, chiefly of small dimensions will be found. Some-in order to identify species, and to decide upon times however, the matter of the shell has entirely those which are new, or peculiar to our own fordisappeared, leaving a distinct cast or impression mation. That many such exist, I have every reain the earth, by which its specific character may son to believe, and with future leisure it is hoped aften be ascertained. Immediately above this that they will be named according to the fashion stratum is a heavy deposite of what Mr. Ruffin of the day, and described in the appropriate place. has described as gypseous earth.* Large masses It will however be of real value to the reader, in of crystalized gypsum, and sometimes the most any inquiries which he may institute, in reference beautiful groups of perfect crystals of this sub- to this formation, to obtain some general idea of stance, are disseminated throughout this layer. It the characters of two or three of the more conspicwas this portion of the formation which Mr. Ruf-uous and characteristic shells. The observer will fin conceived to be identical with the green sand perhaps be able to recognize the following:of New Jersey. In color, this stratum varies from a greenish yellow to a brown. Besides a considerable proportion of green sand, it contains, in addition to the crystalized gypsum, a notable amount of this substance in a subdivided state, and seemingly occupying the place of the shells which were formerly present, and have been decomposed under the chemical agency of some substance which filtrated in solution through the mass. Incumbent upon this bed is a thin layer of very pure white clay, of a texture which would 2nd. Ostrea sellaformis, or saddle-shaped oysrecommend it to various useful purposes. Over-ter. This shell is very peculiar, having, when lying the clay in some places, is a stratum of shell full grown, such a lateral extension on each side as marl in a very subdivided state, containing masses to present, when the hollow of the shell is turned of casts and shells approaching to the hardness of rock. This is the uppermost layer of the eocene

1st. The cardita planicosta. This shell is of various sizes, rarely however equalling that of the clam. In form it bears some resemblance to that shell; but on the convex side a number of flattened ridges run from the knobbed extremity near the hinge, spreading from each other and enlarging as they approach the margin. The hinge part of the shell is very thick. This shell, occurs abundantly in the eocene or lower tertiary of Europe, and also in that of Alabama.

down, a very distinct resemblance to a saddle with its two depending flaps. It is found abundantly in the eocene of Alabama.

3rd. Fusus longaevis, a small shell less than The term "gypseous earth," used in the article re- an inch in length, and resembling in gener ferred to above, was applied not to a part, (as here sup- those which are commonly called conch It a posed,) but to the whole of that formation which Mr. however flattened down on one side as it 'thei Rogers has since shown to be of "green sand." But been subjected to pressure. This shell occur nit was also stated, that by the general application of dantly in the eocene of Europe-but I bel ve Les that term to the extensive beds which seemed to have not until now been discovered in the corresponding had a common origin, (and formerly, the same chemi-formation of this country. cal composition,) it was not intended to convey the opinion that all this earth contained sulphate of lime, either in crystals, or finely divided. On the contrary, that ingredient was said not to be present, in any perceptible quantity, in but very few parts of the great body of what was there called "gypseous earth."See Farmers' Register, Vol. I. p. 208.-ED.

numbers in such of the eocene localities
These three fossils, which are all found in great
" Vir-
ginia as I have examined, are sufficient to den-
tify the formation wherever they may be descov
ered. But as already indicated, they are accon..
panied by a variety of other shells, a large pro-

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on of which, would appear to be peculiar to faction to find that the suggestions based upon particular region. It would seem that the general geological considerations, which were eorene of Virginia though agreeing in most re- presented in my former paper, have already been pects with that of Alabama, contains some so actively and ably followed up by this enlightenfoss is found also in the Paris eocene, and which ed and diligent observer. Of the identity of some e absent from that of Alabama. of the green sand deposites described in his report,

In most of the specimens of marl from this re- with that now ascertained to exist in the eocene gion hitherto examined, besides a large amount of of Virginia, I am as yet by no means convinced; green sand, I have found a considerable propor- but a minute geological examination, such as that tion of gypsum, and in some of them as much as already instituted in Maryland, and that which is forty or fifty per cent. of carbonate of lime. Spe- looked to with some interest in Virginia, cannot cimens received from Dr. Corbin Braxton, at fail to throw very useful light on this, as well as all the Piping Tree, were found to contain, along with the other important deposites in the tide-water much green sand, a great amount of the carbo- region of the two states. Mutual benefit would nate of lime, and some gypsum. Judging from arise from the co-operation of surveys, conducted its composition and texture, it must be looked up- at the same time in the two adjoining territories, on as a very valuable manure. At Coggin's and in this way the interests of the states, as well Point, the lower stratum before described, contains as those of science, would be most effectually and from sixty to seventy per cent. of the green sand, speedily promoted.

with a small proportion of carbonate of lime, and To the very meagre details, in relation to the occasionally a little gypsum. The next deposite green sand, presented in this communication, I above, (the gypseous earth) abounds in gypsum, may hope ere long to be enabled to add the results but contains less green sand than the former. Of of extensive and minute personal observation in this ingredient, however, it still possesses a very the interesting region in which the eocene formaconsiderable proportion. In alluding to the power- tion has been detected. In the mean time, the ful effects of the gypseous earth, in a trial which progress of inquiry may be greatly furthered by he made, the author of the Essay on Calcareous the friendly aid of those who, from their residence Manures describes them as much greater than in the region in question, will have it in their powcould be accounted for by the proportion of gyp-er readily to collect specimens of shells or earth, sum present, and hence throws out the suggestion and to transmit them to me for inspection. I that some other fertilizing ingredient was contain-would therefore, earnestly solicit assistance of this ed in the earth. This additional effect must doubt-kind, and in return, I will gladly communicate the less be ascribed to the presence of the green results of any observations I may be thus enabled sand. to make. To urge the importance of this, and

In prosecuting the geological survey of Ma- other similar inquiries, would now no longer seem ryland, Professor Ducatel has been enabled to ascer- to be necessary-since a large portion of the intain the existence of a green sand deposite through- telligence and enterprise of our state appears out an important district of that state. Of its ex-prompt to recognise their value, and interested istence on both sides of the Potomac I was al-in furthering their active and successful prosecuready fully aware-and it affords me much satis- tion.

WM. B. ROGERS.

ERRATA.

Page 4, in date of preface, for "1834" read "1832."

5, at the end of the advertisement to 2d ed. insert date, “April 1835.”

19, col. 1, 14th line-for "forty-seven” read “fifty-seven."

81, col. 2, 1st line of the note-for "translation," read "transition."

In the marks of reference to Appendix

Page 49, col. 1, line 47, after "Appendix H." add "and S."
58, col. 1, line 48, erase reference to “Appendix K.”
61, col. 2, line 16, for "Appendix L," read "K.”
68, col. 2, line 60, for "Appendix P." read "Appendix E."

VTR = 1969

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