being well founded, that the contrary may be
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 safely affirmed

 The common deGnitiOn of mart, given us by the best writers on fossils, ls-that It IS composed of clay, sand, and lime, very lntl- mately but unequally mixed, slightly cohe- rent, not duclile, but stiff, or viscld, when moist: most easily dillusible in, and disu nited by, water, or even by exposure to the air, and by 1t reduced to soft, loose, lneo- besiye mass; for the most part composed of nothing more than calcareous earth, in which is chief vaiiie consists, combined with a lit- tie mineral oil, clay, and sometimes with linle ochre, or iron. It is also generally coll sdered characteristic of marl, that 1t effer vesces with acids, though to that various ex- captions have been discovered; from which it has been supposed, that, when deprived of that test, 1t contains no calcareous matter, yet it it is found to produce melioratlng el- fects upon the soil. Notwithstanding this summary description, it's appearance IS, how ever, as varied as its properties, being ot CO., Tor nearly pure white, to the darkest shades of brown and red, inerveined with blue and yellow. It also exists in different kinds of land, is seldom found as stratum of much length, but generally in detached masses at various depths, sometimes ill wide and dense perpendicular layers, at others Ill streaks, running in lines parallel with the horizon, or again intersecting each other at right an gles, usually resting on sand or gravel, and is classed, according to it's qualities, into the 1 following distinct species

 l. Clayey marl, which improves sandy land, and seems ~t1~aet as clay, in changing the nature of the soil. In land consisting of mixture of sand and loam, or of sand and gravel, then, the application of this mari has been found peculiarly advantageous; and on all poor and thin sandy soils. there is this | further advantage in it's use-that, from the large proportion of clay which 1t usually contains, 1t adds to their bulk and firmness, and thus has tendency to bring them to that medium state which is the most favora- ble to the purposes of vegetation. It is more soft and unctuous than clay; indeed, upon slightly cutting 1t, 1t becomes so flexible, thai it may be kneaded like dough or paste though, when the moisture eyaporates, il falls into pieces. 1t, therefore, blends easily with the soil, and partaking more largely oi calcareous matter, it's effects, though slow. are in all=tho latter cases more fertilizing, 2 ?. Sandy marl, which is far more frequent in Ireland than in any part of England, and is commonly found Ill pits of llmestone-gravel, whence 1t is in that country usually called limestone-sand It is seldom clammy or unctuous, like the clay-marl, nor does it ad- here to the tongue, but crumbles between the fingers, and feels gritty; when exposed to the air and moisture, 1t slowly chips and mouders; and 1t partakes of some extra neous mixtures. It's color Is sometimes like that of lead, or brown, approaching to black, and at others blue. As implied by its name, 1t contains an excess of sand over that of clay for, upon analyzing it, the proportion of the former has, in most cases, been found to be from 50 to 80 per cent; and 1t does not eflervesee with acids so quickly as the argillaceous marls It possesses but a small degree of tenacity, and it has proved an ex- cellent manure for clayey soils, mellowing their stiffness, and rendering them easier to work

 3. tSiaty or stony marl, to which class, also, properly belongs that which is called rotten Limestone, is chiefly appiie,i to ireayy land Its operation is slow, but very lasting !; land, forty years after it has been laid on, having been found to bear closer and bet ter crop of grass than that which had been recently applied.

 1. Shelly marl, which is evidently pro- duced by the remains of testaceous fish, which, dying in their sireiis, become, in the process of time, converted into calcareous earth; and their bodies, when decomposed, furnish a kind of mould composed of animal substance, which is no doubt analogous to the effect of dung. it is, therefore, highly ferti- lizing, when iudiciously applied, to soils of every kind, which are either in themselves dry, or which have been properly drained

 Such are the most common denominations by which mari is usually distinguished, 1 though 1t is susceptible of many subdivisions by those who affect to treat the subject scen- tfically. It is, however, more frequently classed under the sole characters of siiccoas, argiUdceous, or calcareouS, according as sand, clay, or lime predominates in its com position; but for all practical purposes, it may be sufficient to divide 1t into earth-marl and sheH-marl.

 Library ot Useful Knopledge.

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