8

A DISCOURSE

Of Marl (a substance between clay and chalk, of a cold, sad nature)we have seldom such quantities in layers as we have of the forementionedEarths; but we commonly meet with it in places affected to it, and it istaken out of pits at several depths, and of divers colours, red, white,grey, blue, all of them unctuous, of a slippery nature, and differing ingoodnefs ; for, being pure and immixed, it sooner relents after a shower,and when dried again, slackens and crumbles into dust, without indura-tion, and growing hard. All the kinds are profitable for barren grounds,as abounding with nitre d .

Lastly, Chalk. This is likewise of several kinds and colours; hard,soft, fine, coarse, abstergent, slippery, and marly, and apt to difsolve withthe weather into no unprofitable manure. Some kinds have a sandish,others a blacker and light surface ; and there is a sort which producessweet grafs and aromatic plants, and some so rank, especially in the valliesof very high hills, as to feed not only sheep, but other cattle, to greatadvantage, as we may see in clivers places among the clowns of Sufsex.

But it has a peculiar virtue above all this, to improve other lands, as weshall come to show.

I forbear to speak particularly of Fullers-Earth , Tobacco-pipeClay,dry and astringent, the white Cimolia, and the several fictile clays, be-cause they are not so universal and serviceable to the plough and spade ;much lefs of Terra Lemnia, Chia, Melitensis, Hetrusca, and the rest ofthe Sigillata:; nor of the Boles, Rubrics, and Ochres, Figuline, Stiptic,Smegmatic, &c. as they are diversely qualified for several uses, medicinaland mechanical, but content myself with those I have already enume-rated e .

* Whoever is'desirous of obtaining a just and philosophical idea of marl, may consultDr- Ainslie’s account of that substance, as insertedpn the Georgical E/say. In the same workthere is a most useful Efsay by the ingenious Mr. Henry, of Manchester, on the mannerof compounding factitious marl, for the use of such farmers as reside in countries wheregenuine marl cannot be obtained. Sand and calcareous Earth plentifully bestowed uponheavy clay land, will, for a time, convert the surface, to the depth of some inches, into akind of Marl . It were to be wished that the mixture of opposite soils was more attendedto by the farmer, and this happy consequence would follow, that over stiff and adhesivelands would be made tender, and over sandy lands would have a texture given them.

* Earths consist of very minute and almost impalpable particles, cohering very slightly