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proportion of carbonate of magnesia, as well as of carbonate of lime, has been found in Hanover. Professor Rogers, of William and Mary College, has discovered in many of the marls of Lower Virginia, some proportion of the "green sand" of geologists, or what is itself called "marl," (another misapplication of that name,) in New Jersey, and which has there been found highly valuable as manure, though containing not a particle of the carbonate of lime, which constitutes the sole value of however interesting may be the discovery of these different ingredients, and however valuable they may prove as manures, still they are not to be considered as treated of in this essay under any general observations on marl, which are intended to be applied simply to manure, the only useful ingredient of which, is the carbonate of lime. [Appendix O.]

presence of this deposite, it may be inferred, that | tion of gypseous marl, (page 48:) and some others it lies beneath nearly every part of our country have been discovered since the publication of that between the sea and the granite ridge which forms statement. A kind of earth containing a large the falls of all our rivers. It is exposed, where it rises, and where cut through by the deep ravines of hilly land, and the courses of rivers-and concealed by its dips, and the usual level surface of the country. The rich tracts of neutral soil on James River, such as Shirley, Westover, Brandon, and Sandy Point, seem to have been formed by alluvion, which may be termed recent, compared to that of our district in general: and in these, no marl has been found, though it is generally abundant in the adjacent higher lands.* Fresh-shells and calcareous manures in general. But water muscle shells are sometimes found in thin layers (from a few inches to two feet thick) both on those lands, and others-but'generally near the surface, and always far above the deposite of sea shells, found under the high land. These two layers of different kinds of shells are separated by a thickness of many feet of earth, containing no shells of any kind. From these appearances, it would seem that this tract of country was, for ages, the bottom of the sea-then covered by earththen the bottom of a fresh-water lake-and finally made dry land. Muscle shells are richer than the others, as they contain much gelatinous and enriching animal matter. On this account, the earth with which muscle shells are found mixed, is a rich black mould. Most persons consider these beds of muscle shells as artificially formed by the Indians, who are supposed to have collected the muscles, for food, and left the shells, where the fish were consumed. There are some strong reasons which may be adduced both to sustain and to oppose this opinion. But whatever may be the origin of these collections of muscle shells, it does not affect their qualities as manure for the soils in which they are found, or for others to which they may be removed.

More than forty kinds of sea shells are found in the beds of marl that I have worked without counting any of very small size. Many kinds would escape common observation, and still more would require the aid of a magnifying glass to be distinguished. Generally the shells are whole, but are much broken by digging, and the after operations. The white shells are rapidly reduced, after being mixed with an acid soil-but some gray kinds, as scallop, and a variety of oyster, are so hard as to be very long before they can act as manure. Some beds, and they are generally the richest, have scarcely any whole shells, but are formed principally of small broken fragments. Of course the value of marl as a manure depends in some measure on what kinds of shells are most numerous, and their state of division, as well as upon the total amount of the calcareous earth Neither the fossil sea shells, nor the earth mixed contained. The last is however by far the most with them are supposed to contain any putrescent important criterion of its value. The most exmatter-and this manure has been considered perienced eye may be much deceived in the throughout this essay as being valuable only as strength of marl, and still more gross and dangercontaining calcareous earth. This, no doubt, is ous errors would be made by an inexperienced the only ingredient of any worth, in the great marler. The strength of a body of mark often majority of cases. But sometimes there are other changes materially in sinking a foot in depth-alingredients-which must be considered merely as though the same changes may be expected to ocexceptions to the general rule. One of these ex-cur very regularly, in every pit sunk through the ceptions has already been stated, in the descrip

same bed, Whoever uses marl, ought to know how to analyze it, which a little care will enable any one to do with sufficient accuracy. The methods described in Chap. V. for ascertain*It seems however, from facts learned since the pub-ing the proportions of calcareous earth in soils, lication of the passage above, that marl is, or has been, will of course serve for the same purpose with below these alluvial lands, though only at considerable marl. But as more minute directions may be nedepths. This does not contradict the opinion express

ed that no marl is to be found in such land. The de-cessary for many persons who will use this maposites referred to were of much more ancient forma-nure, and who ought to be able to judge of its vation, and have been covered by the very different and lue, an additional article on this subject will be peculiar bodies of land which now form not only the given in the Appendix. [See P.] surface, but a depth as low as the level of the river. Benjamin Harrison, Esq., of Berkley, (a tract of such land as is above described,) has found on the river beach, and dug deeply into, a body of the earth described at page 49, which evidently was once full of shells, though now retaining neither shells nor any trace of carbonate of lime, except some few stony and insulated It has also been very recently stated, that fossil shells have been found at the level of the river at Curl's Neck in Henrico. These are interesting facts, which ought to encourage searches for such deposites in every part of the low country,

masses.

For want of attention to this only safe guide, gross errors are often committed, and losses continually sustained. By relying on the eye only, I have known marl, or rather a calcareous sand, rejected as worthless, and thrown off at considerable cost of labor, to uncover worse marl below, where whole shells were visible: and on the contrary earth has been taken for marl, and used as such, which had no calcareous ingredient whatever. The best marls for profitable use are generally such as show the fewest whole shells, or even large

to work. Unless very poor, all marls are sufficiently firm and solid for the sides of the pit to stand, when dug perpendicularly.

If marl reaches the surface any where, it may be most easily found by examining the beds of streams passing through the lowest land, or deepest ravines. A few of the smallest particles of shells found there, will prove that the stream passes through marl somewhere above; and a careful examination continued towards the source, will scarcely fail to discover where the bed lies. Its usual direction is horizontal, or very little inclined and therefore if discovered any where along the sides of a narrow valley, it may generally be found by digging on the opposite side, or elsewhere not very distant at the same elevation on the hill-side: and it is always nearer the surface on swells, or convex parts of the hill-side, than where it retreats and forms hollows. In the more level parts of the country, the marl sometimes is very near the surface of the lowest land, and yet is not visible any where. In such situations particularly, a cheap and convenient auger may be used with much advantage in searching for marl: and it is also useful to try the depth or quality of a bed, even when its surface has been found. This tool may be made by welding a straight stem, For any extensive operation, it is much cheaper half an inch square and six or seven feet long, to to take off a cover of earth, twelve feet thick, to oba common screw auger of about one inch and a tain marl of equal depth, than if both the covering half bore. If it has been so much worn as to be earth and marl were only three feet each. Whethuseless as a carpenter's tool, it will serve for boring er the cover be thick or thin, two parts of the opin earth. A cross-piece for a handle should be eration are equally troublesome, viz. to take off' fixed to slide over the stem, and be fastened by a the mat of roots, and perhaps some large trees on small screw at different elevations, as most con- the surface soil, and to clean off the surface of the venient. Other pieces may be added to the stem, marl, which is sometimes very irregular. The attached by joints, so as to bore twelve or more greater part of the thickest cover would be much feet deep. Dr. W. Cocke of Sussex, to whom I easier to work. But the most important advanam indebted for this simple but useful tool, wastage in taking off earth of ten or more feet in enabled by its use to find a very valuable bed of thickness, is saving digging, by causing the earth marl which was no where visible at the surface, to come down by its own weight. If time can be and which he has since been using to great ex-allowed to aid this operation, the driest earth will tent and advantage.

fragments-and would be passed by unnoticed in some cases, or considered only as barren sand, or equally worthless clay. But even if such mistakes as these are avoided, every farmer using Where a bed of marl is dry and not covered by marl, without analyzing specimens frequently much earth, no directions are required for the pit and accurately, will lose by applying it in quanti-work-except it be, that the pit should be long ties either too great or too small. enough to allow the carts to descend to the bottom (when finished) and to rise out on a slope sufficiently gradual. This will prevent the necessity of twice handling the marl, by first throwing it out of the pit, and then into the carts, which must be done, if the pit is made too short, or its ends too steep, for the loads to be drawn out. No machine or coutrivance will raise marl from the bottom of a pit, or a valley, so well as a horse-cart-and no pains will be lost, in enlarging the pit, and graduating the ascent out of it, to attain that object. As marl usually shows on a hill-side, but little earth has to be moved to uncover the first pit. But the next, and each successive cover of earth, will be more thick, until it may be necessary to abandon that place and begin again eisewhere. But the quantity of covering earth need not be regarded as a serious obstacle, if it is not thicker than the marl below it. While that is the case, one pit completed will receive all the earth thrown from an equal space, for commencing another. When this proportion of earth is exceeded, it is necessary to carry it farther, by either carts or scrapers, and the labor is greatly increased.

move, my labor was made ten-fold heavier, by digging altogether. The surface bore living trees, and was full of roots-there was enough stone to

mostly fall, by being repeatedly undermined a By proper examinations marl may be found at little. But this is greatly facilitated by the oozing or near the surface through a vast extent of the water, which generally fills the earth lying immetide-water region of the United States, where it diately on beds of wet marl. In uncovering a bed has not yet been noticed. But still, under most of this description, where the marl was to be dug lands it probably does not approach within twenty-fourteen feet, and ten to twelve feet of earth to refive or thirty feet of the surface, and if reached by digging, would be covered by water, so as greatly to increase the difficulty of obtaining it from such depths. Will these obstacles always debar from the benefit of this treasure half the great region under which it lies? I think not: and though it would be ridiculous now to propose such undertakings, it will at some future time be found profitable to descend still greater depths for good marl: and shafts will be sunk and the water and marl drawn out by horse power, or by steam engines, and the excavation carried on in the same manner as is done in coal mines,

Our beds of marl are either of a blue, or a yellowish color. The color of the first seems to have some connexion with the presence of water, as this kind is always kept wet, by water slowly oozing through it. The yellow marl is sometimes wet, but more generally dry, and therefore easier

*The blue color of marl is not caused by merely the presence of water, or there would be no wet yellow marl. When both blue and yellow marl are seen in the same bed, the blue is always at bottom-and the line of division between the colors is well defined, and there is seen no gradual change of one to the other. I have lately observed (in 1834) that as intense and perfect a blue color as marl has ever been known to have, was given to what had been dry yellow marl, by its being used as a thick flooring for a stable yard, and kept covered with the rotting manure, and penetrated by its liquid oozings, which the marl was there placed to save. It may be inferred from this fact, that blue marls have received their color from some vegetable extract or other putrescent matter, dissolved in the water passing through the bed.

keep the edges of the grubbing hoes battered- drain, will run to the outside, the dip of which and small springs and oozing water came out should lead to the lower main drain. After this every where, after digging a few feet deep. A form is given to the surface of the area, very little considerable part of the earth was a tough, sticky attention is required to preserve it; for if the succlay, kept wet throughout, and which it was equal-cessive courses are dug of equal depth from side to ly difficult to get on the shovels, and to get rid of. Some years after, another pit was uncovered on the same bed, and under like circumstances, except that the time was the last of summer, and there was less water oozing through the earth. This digging was begun at the lowest part of the earth, which was a layer of sand, kept quite wet by the water oozing through it. With gravel shovels, this was easily cut under from one to two feet along the whole length of the old pit-and as fast as was desirable, the upper earth, thus undermined, fell into the old pit: and afterwards, when that did not take place of itself, the fallen earth was easily thrown there by shovels. As the earth fell separated into small but compact masses, it was not much affected by the water, even when it remained through the night before being shoveled away. No digging was required, except this continued shoveling out the lowest sand stratum, and whether clay, or stones, or roots, were mixed with the falling earth, they were easy to throw off. The numerous roots which were so troublesome in the former operation, were now an advantage, as they supported the earth sufficiently to let it fall only gradually and safely; and before the roots fell, they were almost clear of earth. The whole body of earth, notwithstanding all its difficulties, was moved off as easily as the driest could have been by digging altogether.

side, the previous dip will not be altered. The sides or walls of the pit should be cut something without the perpendicular, so that the pit is made one or two feet wider at bottom than top. The usual firm texture will prevent any danger from this overhanging shape, and several advantages will be gained from it. It gives more space for work-prevents the wheels running on the lowest and wettest parts-allows more earth to be disposed of, in opening for the next pit-and prevents that earth tumbling into the next digging, when the separating wall of marl is cut away. The upper drain of the pit, which takes the surface water, will hang over the one below, kept for the oozing water. The former remains unaltered throughout the job, and may still convey the stream when six feet above the heads of the laborers in the pit. The lower drain of course sinks with the digging. Should the pit be dug deeper than the level of the receiving ditch can be sunk, a wall should be left between, and the remainder of the oozing water must be conducted to a little basin near the wall, and thence be baled or pumped into the receiving ditch. The passage for the carts to ascend from the pit should be kept on a suitable slope-and the marl forming that slope may be cut out in small pits, after the balance has been completed.

If the marl is so situated that carts cannot be driven as low as the bottom, then the area must be cut out in small pits, beginning at the back part, and extending as they proceed, towards the road leading out of the pit.

On high and broken land, marl is generally found at the bottom of ravines, and separated from the field where it is to be carried, by a high and steep hill-side. The difficulty of cutting roads in such situations, is much less than any inexperienced person would suppose. We cannot get rid of any of the actual elevation-but the ascent may be made as gradual as is desired, by a proper location of the road. The intended course must be laid off by the eye, and the upper side of the

In working a pit of wet marl, no pains should be spared to drain it as effectually as possible. Very few beds are penetrated by veins of running water, which would deserve the name of springs -but water oozes very slowly through every part of wet marl, and bold springs often burst out immediately over its surface. After the form of the pit, and situation of the road are determined, a ditch to receive and draw off all the water, should be commenced down the valley, as low as the bottom of the pit is expected to be, and opened up to the work, deepening as it extends, so as to keep the bottom of the ditch on the same level with the bottom of the marl. It may be cheaper, and will serve as well, to deepen this ditch as the deepen-road marked. If it passes through woods, it will ing of the pit proceeds. After the marl is uncovered the full size intended for the pit, (which ought to be large enough for carts to turn about on,) a little drain of four or five inches wide, and as many deep, (or the size made by the grubbing hoe used to cut it,) should be carried all around to intercept the surface or spring water, and conduct it to the main drain. The marl will now be dry enough for the carts to be brought on and loaded. But as the digging proceeds, oozing water will collect slowly; and aided by the wheels of loaded carts, the surface of the firmest marl would soon be rendered a puddle, and then quagmire. This may easily be prevented by the inclination of the surface. The first course dug off, should be much the deepest next the surface drain, (leaving a margin of a few inches of firm marl, as a bank to keep in the stream) so that the digging shall be the lowest around the outside, and gradually rise to

be necessary to use grubbing hoes for the digging. With these, begin at the distance of four or five feet below the marked line, and dig horizontally onward to it. That earth is to be pulled back with broad hoes, and laid over a width of three or four feet below the place from which it was taken.

a

b

the middle of the area. Whatever water may Thus the upper side of the road is formed by cutfind its way within the work, whether from oozing,ting down, and the lower side by filling up, with rain, or accidental burstings of the little surface the earth taken from above.

The annexed figure will prevent these directions, load, which advantage will be found on trial much being misunderstood. The straight line from a to more important than would at first be supposed. b represents the original slope of the hill-side of If carts of common size are used, the careless lawhich the whole figure is a section. The upper borers will generally load too lightly-yet someend of the dotted part of the line is in the mark times will injure the horse by putting in a load for laying off the upper side of the road. The up- much too heavy. The small-sized cart-bodies per triangle is a section of the earth dug out of the prevent both these faults. The load cannot be hill-side, and the lower triangle, of the part formed made much too heavy-and if too light, the farby its removal. The horizontal line is the level mer can detect it at a glance. Where there is a of the road formed by cutting in on the upper, and hill to ascend, five heaped bushels of wet marl is filling up on the lower side. After shaping the a sufficient load for a horse. If the marl is dry, or road roughly, the deficiencies will be seen and may the road level, six bushels may be put in the same be corrected in the finishing work, by deepening carts, by using tail-boards.

some places and filling up others, so as to gradu- Strong laborers are required in the pit for digate the whole properly. A width of eight or nine ging and loading: but boys who are too small for feet of firm road, will be sufficient for carting marl. any other regular farm labor, are sufficient to If the land through which the road is to be cut is drive the carts. Horses or mules kept at this work not very steep, and is free from trees and roots, soon become so tractable, that very little strength the operation may be made much cheaper by using or skill is required to drive them. the plough. The first furrow should be run along All these hints and expedients, or perhaps betthe line of the lower side of the intended road, and ter plans, would occur to most persons before they turned down hill: the plough then returns empty, are long engaged in marling. Still these directo carry a second furrow by the first. In this tions may help to smooth the obstructions in the manner it proceeds-cutting deeply, and throwing way of the inexperienced-and they will not be the slices far, (both of which are easily done on a entirely useless, if they serve to prevent even small hill-side,) until rather more than the required losses of time and labor.

width is ploughed. The ploughman then begins

again over his first furrow, and ploughs the whole My task is at last completed. Whether I shall over as at first-and this course is repeated per- be able to pursuade my countrymen to prize the haps once or twice more, until enough earth is cut treasures, and seize the profits which are within from the upper and put on the lower side of the road. their reach, or whether my testimony and arguAfter the first ploughing, broad hoes should aid ments shall be fruitless, soon or late, a time must and complete the work, by pulling down the earth arrive when my expectations will be realized. The from the high to the low side, and particularly injuse of calcareous manures is destined to change those places where the hill-side is steepest. After a large portion of the soil of Lower Virginia from the proper shape is given, carts, at first empty, and barrenness to fertility-which, added to the advanthen with light loads, should be driven over every tages we already possess-our navigable waters part of the surface of the road, until it is firm. If and convenient markets, the facility of tilling our a heavy rain should fall before it has been thus lands, and the choice of crops offered by our clitrodden, the road would be rendered useless for a considerable time.

mate-will all concur to increase ten-fold the present value of our land, and produce more farming Tumbril carts drawn by a single horse or mule, profit than has been found elsewhere on soils far are most convenient for conveying marl short dis- more favored by nature. Population, wealth, and tances. Every part of the cart should be light, learning, will keep pace with the improvement of and the body should be so small as only to hold the soil and we, or our children, will have reason the load it is intended to carry, without a tail-board. to rejoice, not only as farmers, but as Virginians, This plan enables the drivers to measure every

and as patriots.

APPENDIX.

Part III.

Most of the articles which will be given in this late of lime is also supposed to be highly valuable Appendix, are deemed important to the parts of as a manure, and far more abundant. Many the Essay to which they refer, as furnishing more other salts of lime are known to chemists: but full explanation, or proof, of positions there main- their several qualities, as affecting soils, are entiretained: but they are not absolutely essential to the ly unknown-and their quantities are too small, text-and have therefore been thrown into this and their presence too rare, to require consideraplace and form, both for convenient reference, and tion. If all the numerous different combinations to avoid interrupting the train of argument, or the of lime, having perhaps as many various and unconnexion of facts, to those readers who may not known properties, had not been excluded by my need views so extended. But, though a regu- definition of calcareous earth, continual exceptions lar recurrence to these notes may not be ne- would have been necessary, to avoid stating what cessary as they are referred to in the foregoing was not meant. The carbonate of lime, to which text-and generally had better be postponed for I have confined that term, though only one of an after and separate reading—still it is believed many existing combinations, yet in quantity and that most of them will be found either useful or in- in importance, as an ingredient of soils, as well as teresting to those who may have read with appro- a part of the known portion of the globe, very far bation what precedes them. This form will be exceeds all the others. convenient both to those who may choose to pass But even if calcareous earth, as defined and over, as superfluous, any particular portions, and and to attract to these notes the attention of other readers, who may want the more full statements and proofs offered.

[NOTE A. Page 9.]

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limited, is admitted to be the substance which it is proper to consider as one of the three earths of agriculture, still there are objections to its name, which I would gladly avoid. However strictly defined, many readers will attach to terms such meanings as they had previously understood: and the word calcareous has been so loosely, and so differently applied in common language, and in THE DIFFERENT IMPROPER SIGNIFICATIONS agriculture, that much confusion may attend its OF THE TERM "CALCAREOUS EARTH.' use. Any thing "partaking of the nature of lime" is "calcareous," according to Walker's Dictionary: The definition of calcareous earth, which con- Lord Kames limits the term to pure lime*—Davyţ fines that term to the carbonate of lime, is certainly and Sinclair, include under it pure lime and all liable to objections, but less so than any other its combinations-and Kirwan,|| Rozier, and mode of arrangement. It may at first seem ab- Young,§ whose example I have followed, confine surd to consider as one of the three principal the name calcareous earth to the carbonate of earths which compose soils, one only of the many lime. Nor can any other term be substituted combinations of lime, rather than either pure lime without producing other difficulties. Carbonate of alone, or lime in all its combinations. One or the lime would be precise, and it means exactly the other of these significations is adopted by the same chemical substance: but there are insuperahighest authorities, when the calcareous ingre-ble objections to the frequent use of chemical dients of soils are described-and in either sense, names in a work addressed to ordinary readers. the use of this term is more conformable with Chalk, or shells, or mild lime, (or what had been scientific arrangement, than mine. Yet much in- quicklime, but which from exposure to the air, had convenience is caused by thus applying the term again become carbonated,) all these are the same calcareous earth. If applied to lime, it is to a sub-chemical substance-but none of these names stance which is never found existing naturally, and would serve, because each would be supposed to which will always be considered by most persons mean such certain form or appearance of calcaas the product of the artificial process of calcina-reous earth, as they usually express. If I could tion, and as having no more part in the composi- hope to revive an obsolete term, and with some tion of natural soils, than the manures obtained from oil-cake, or pounded bones. It is equally improper to include under the same general term all the combinations of lime with the fifty or sixty various acids. Two of these, the sulphate, and the phosphate of lime, are known as valuable manures; but they exist naturally in soils in such minute quantities, and so rarely, as not to deserve to be considered as important ingredients. A subsequent part of this essay will show why the oxa

*Gentleman Farmer, page 264, (2d Edin. Ed:)
Agr. Chem. page 223, (Phil. Ed. of 1821.)
Code of Agriculture, page 134, (Hartford Ed.
1818.)

|| Kirwan on Manures, Chap. 1.
"Terres"-Cours Complet d'Agriculture Pratique.
§Young's Essay on Manures, Chap. 8.

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