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 forementioned 

 earths ; but we commonly meet with it in places affected to it, and it is 

 taken out of pits at several depths, and of divers colours, red, white, 

 gray, blue, all of them unctuous, of a slippery nature, and differing in 

 goodness ; 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 



Lastly, chalk. This is, likewise, of several kinds and colours ; hard, 

 soft, fine, coarse, abstergent, slippery, and marly, and apt to dissolve with 

 the weather into no unprofitable manure. Some kinds have a sandish, 

 others a blacker and light surface ; and there is a sort which produces 

 sweet grass and aromatic plants, and some so rank, especially in the 

 valleys of very high hills, as to feed not only sheep, but other cattle, to 

 great advantage, as we may see in divers places among the downs of 

 Sussex. But it has a peculiar virtue above all this, to improve other 

 lands, as we shall come to shew. 



I forbear to speak particularly of fullers'-earth, tobacco-pipe clay, 

 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 less of terra lemnia, chia, melitensis, hetrusca, and the rest of 

 the sigillatee ; nor of the boles, rubrics, and ochres, figuline, stiptic, 

 smegmatic, &ic. as they are diversely qualified for several uses, medicinal 

 and mechanical, but content myself with those I have abeady enume- 

 rated ^ 



■3 Whoever is desirous of obtaining a just and philosophical idea of marl, may consult 

 Dr. Ainsiie's account of that substance, as inserted in the Georgical Essays. In the same work, 

 there is a most useful Essay by the ingenious Mr. Henry, of Manchester, on the manner 

 of compounding faclitious marl, for the use of such farmers as reside in countries where 

 genuine marl cannot be obtained. Sand and calcareous earth plentifully bestowed upon 

 heavy clay land, will, for a time, convert the surface, to the depth of some inches, into a 

 kind of marl. It were to be wished that the mixture of opposite ^oils was more attended 

 to by the farmer, and this happy consequence would follow, that over-stiff and adhesive 

 lands 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 



