logical value of the mineral wealth of the country rather than purely scientific relations. To carry out this plan would involve some expenditure for the fitting up of necessary shelving, &c., for the specimens.

GREENSAND MARLS.

Of the mineral analyses performed during the year those of marls much exceeded all others. These marls were not those of the alluvial, or, as it is sometimes called, quaternary formation, as the name might imply; but were derived either from the .cretaceous or the tertiary; and, as many greensand marls from Maryland and Virginia were among the number, some remarks concerning them, as regards their pecularities and contrast with other beds of same age further north, may not be out of place.

THEIR POSITION AND GEOLOGICAL RELATION.

The greensand beds of the Atlantic States are a very important geoiogical formation, whether we consider them as occupying a large tract of country or as affording a valuable amendment to the soil which they underlie. Extending in a gentle and continuous curve along the seacoast, they are found in every coast State from the Hudson River to the Mississippi. The beds have a very general trend north-northeast and south-southwest, and a similar dip, being about twenty feet to a mile in New Jersey, and almost precisely the same in Mississippi; showing a great uniformity in the causes which led to their deposition and elevation, and in the conditions governing them. Occurring at the close of the cretaceous period, owing to the absence of cementing material originally present, or subsequently percolating, they have never consolidated, and are still beds of sand, (clayey and calcareous sand,) differing in no physical respect from the alluvial and later beds, which cover them to the depth of several feet.

Although the lithological character of the beds is not the same in the northern and the southern extremity of the deposits exposed, yet their identity can be at all times recognized by the fossil shells most abundantly present, and which are by far the most uniform in occurrence. When the manner of deposition of this sand over so large a tract of country is examined, it is found that the amount of material varies considerably in thickness, generally diminishing the further south it is examined.

In New Jersey these marl beds occupy a very narrow belt of land from four to sixteen miles wide, from the ocean shore near Sandy Hook (New York Bay) to Salem, on the Delaware. A sandy soil, destitute of diluvium, covers the region, which has a strike south 55° west, and a dip southeast about twenty feet per mile. This formation is composed of six beds, three of which are true greensand layers, and three are beds of marine sand separating the others. In Maryland and Virginia it is probable that these three beds or their equivalents may exist, but they have not been accurately distinguished; and in North Carolina but two of the three have been recognized, the lower bed being formed at Black Rock, and the upper bed at Tarborough, on Tar River, at Colonel Clark's. In the latter place the shell bed, containing pecten, exogyra, belemnites, lignite, and pyrites, is found immediately over the stratum of greensand, which is confined to one bed, or at most to two. In Mississippi but one bed is found as the representative of the three of New Jersey; nor does this single bed exceed in thickness a single bed of the New Jersey deposit.

So much has been already written about the greensand beds of New Jersey that but little is needed to be inserted here. Being the first deposits of this character used as a fertilizer for the soil, and the demand increasing more than the yield, it has for some years back been an article of marketable transport on railways, and is acknowledged to be second to no other mineral fertilizer when it is considered how long a dressing of it is felt upon the land. In that State the greensand is in places, as in Burlington County, mixed with a dark chocolate-colored clay; in Monmouth County generally with a lighter clay and some shells. In beds more to the south the sand increases in amount, while in a few beds here and there the marl appears to have undergone but little mixture with clay or sand, but is almost wholly composed of the green grains which have given the name of greensand to the whole formation. Until lately the great value of this fertilizer was attributed to its constituent potash; but it is now admitted that its value is not due to this source alone, and that it must be shared with phosphoric acid and other constituents. As the pure greensand grains (glauconite) are valuable portions of this manure, efforts have been made, both in this laboratory and elsewhere, to ascertain their exact chemical composition. The variable results are not owing to any intrinsic difficulty in analysis, but to the extreme difficulty of procuring samples sufficiently clean and free from foreign matters for operating upon. By washing and sifting, even though performed many times, it is almost impossible to obtain the green grains perfectly free from admixture with sand and sulphate and also phosphate of lime. This difficulty is mentioned in the final report of the Geological Survey of New Jersey, (1868,) in which appear several examples of analysis of these marls, apparently performed with care, industry, and chemical skill. On page 281 of that report the following occurs as one of the averages of the composition of glauconite:

The

The potash in other analyses varied, running from 7.262 to 9.087 per cent. The analyses excludes all the lime, salts, and the silica in the marl from the constitution of the glauconite, the chief agricultural value of which had been estimated to lie in its potash constituent. The iron exists in both states of oxidation as protoxide and peroxide. amount of greensand grains present in the various marls of New Jersey ranged from 16 per cent. to 90-from 25 to 33 per cent. being the average of many. It is worthy of remark how small an amount of glauconite gives a blue tint to clay or sandy clay-less than 4 per cent. giving a very decided shade of blue.

The foregoing, however, does not represent the true composition or the actual value of the greensand of New Jersey as it is used. In the second annual report of the Geological Survey of that State, 1856, pp. 85-91, several analyses of the greensand marls are given, in all of which two ingredients, additional to those described as entering into

glauconite, are set down-sulphuric and also phosphoric acid-the latter

of which exists in notable proportion.

Squankum marl yields of phosphoric acid.

Pemberton, (No. 1).

Pemberton, (No. 2).

Clementon
Freehold.

New Egypt.

Blackwoodtown
Woodstown..
Marlborough
Shelltown..

4.54 per cent.

1.68 (6

66

The last named is from the clay which underlies the marl, and which, though green in color, contains but few green grains. This phosphoric acid in some specimens exists as phosphate of lime; in others, as phos. phate of iron. The latter probably was its original combination. The presence of pyrites and vegetable matter results in the formation of sulphuric acid, which, acting in the iron phosphate and on the lime carbonate of the shelly portion, liberates the phosphoric acid of the first and unites with the lime of the second; the free phosphoric acid then acts on some lime carbonate to form phosphate of lime. Thus both sulphate and phosphate of lime are introduced into the marl. But whence is the origin of the phosphate of iron? The glauconite does not appear to furnish sufficient to account for the amount given above; indeed, the usual analyses of pure glauconite do not mention phosphoric acid as a constituent. It is assumed by Professor Cook that the phosphate of lime of these sands is a foreign ingredient, and no necessary part of glauconite. "In fact," he states, "the phosphate of lime can easily be distinguished by the eye from the greensand grains with which it is mixed. It does not form any necessary part of the mineral, and may be rejected from the analysis."

The fact of the universal presence of phosphate of lime in the green sand is certainly no proof of its origin in the glauconite; but that the phosphate of lime may be detected by the eye in the mass of the marl as distinct from the green sand has not been verified in the examination of marls in this laboratory. Indeed, the reverse has generally been demonstrated. From a carefully conducted chemical analysis, made in this laboratory by the assistant chemist, Dr. Tilden, upon a sample of greensand marl from Upper Marlborough, Maryland, which contained on an average 50 per cent. of fine angular quartz sand as its only visible admixture, there were found in one hundred parts 1.53 parts of anhydrous phosphoric acid, equivalent to 7.44 per cent. of the probable ferroso-ferric phosphate. The phosphoric acid had not been united with lime in the marl, and must have existed as a phosphate of iron; and, if not a constituent of the glauconite, was present as a phosphatic earth commonly found in this geological formation, and is the parent of the vivianite occasionally found in the stratum.

In the State of Delaware the greensand beds are found crossing its northern border in their course from New Jersey into Maryland. Repetitions of the beds occur in the ravines of St. George's Creek, where the chemical composition is carbonate of lime, greensand, and white silicious sand. Along the line of the canal west of St. George's the bed has yellow clay and micaceous clay mixed with the greensand, giving dif ferent shades of color to the bed. The southern limit is near Cantwell's Bridge, where the marl is found to be mixed with yellow clay, and is

much more ferruginous than elsewhere. In St. George's Hundred a bed of bluish green sand is met with, which is described by Professor Booth, who is the authority here quoted, as being nearly pure glauconite, and yielding, on an analysis:

The presence of the lime and magnesia shows that calcareous detritus has crept into this specimen. The bright green sandy marl of Drawyer's Creek furnishes, on analysis, a nearer approach to the glauconite composition:

Classing the Delaware greensand in two deposits, the calcareous and the glauconitic, which are separated by a bed of yellow sand or sandy clay, it is found that these beds occasionally merge together and separate again. This has been observed in sections of the canal in Delaware. The same occurrence is met with in river cuts in North Carolina. The chemical composition of the beds of course varies in proportion as either the calcareous or glauconitic element preponderates. This is well seen in the analyses of the upper and the lower greensand deposit of Delaware, made by Professor Booth, in which the lime may be taken as the varying substance.

The average thickness in Delaware is about twenty-one feet, increasing in the south to twenty-five feet. The highest amount of carbonate of lime which has been found in the calcareous greensand of this State is twenty-five per cent. These beds enter Maryland from Delaware at the head of Appoquinomink Creek, or near the head of the Sassafras in Kent County, whence it crosses the Chesapeake into Anne Arundel County and Prince George's. In the latter it approaches the line of the District of Columbia, occurring at Marlborough in beds ten to twelve feet thick; thence it passes south through Charles County below Chicomoxen Creek, and enters Virginia at Aquia Creek, in Stafford County. The marls in Maryland and Virginia may properly be considered in this place, as, although not presenting the characters of the true greensand beds, yet they bear a close relation to those found in New Jersey and Delaware. From the samples of all of these marls forwarded from these two States to the department for examination, it would appear that, excepting the beds near upper Marlborough, the strata belong to the lower eocene, as is shown by the fossils occurring through them. They resemble the Delaware marls in the large amount of carbonate of lime which they contain, clearly showing their geological position to be in the cretaceous or chalk formation. This carbonate of lime it not always evident as whole shells or fragmentary portions; but, even when not distinct to the naked eye, constitutes a portion of the mass as a finely coherent powder, so that every stratum of these greensands may be roughly stated as made up of—

Of these the latter element is the most constant; for though it may be found that the bed of one locality differs from the same bed in another in containing less glauconite, yet there is not therefore present more chalk or carbonate of lime. It is then usually found to be more sandy, while sometimes, instead of the whitish quartz grains increasing, a greenish or bluish micaceous sand takes its place. The amount of the glauconite varies, but rarely ever approaches one-third of the whole. More frequently it is less than ten per cent., and in most of those in Prince George's County and Charles's it seldom exceeds three per cent., as shown by elutriation. When this mineral is in so small amount, of course the marl does not pay for its distant transportation; but it is still a benefit to the neighborhood, and it is to be regretted that the State of Maryland and also of Virginia do not awake to the value of these sources of wealth, thus profusely scattered in the very positions where they can be made so highly beneficial. In the localities of the miocene and the upper tertiary beds, and the strata of drift, gravel, and sands, and the quaternary layers which skirt the borders of the ocean-the banks of the large embouchures or bays, as the Delaware and the Chesapeake, the Potomac and other rivers, where a sandy clay constitutes the chief surface soil, and where fertility is to be assured only by the utmost and continued efforts of labor and by manures, the latter being often unattainable or of high price-the marls described would prove very valuable, converting sandy and pine deserts into regions of agricultural wealth rivaling any market garden on alluvial clay. Where exposures are met with, the beds should be cleaned out, examined by some competent person, and the value chemically ascertained. Private enterprise will never take the initiative in this pro