On Manures. 221 



4. Chalk. This calcareous substance, proves a useful ma- 

 nure in many of the southern and eastern districts of England, 

 where it abounds. It is frequently applied in a crude state, 

 spread upon the surface in autumn, and left to be dissolved by 

 the winter's frost. From five to eight waggon loads per acre, 

 are attended with beneficial effects, the benefit of which is felt 

 for fifteen and even twenty years. When calcined, from 100 

 to 200 bushels per acre are applied, but the effects not being 

 lasting, the application requires to be repeated every four or 

 five years ; and as chalk lime, does not exceed in any material 

 degree chalk itself, there is no encouragement to burning it, 

 more especially as calcined limestone, where it can be obtained, 

 is much more effectual. Both chalk and marl are supposed to 

 have the beneficial effects of all the calcareous earths, in giving 

 stiffness and whiteness to straw ( 329 )j as well as rendering the 

 skin of corn thin, and increasing the quantity of its meal (* 3 ). 

 Chalk has a great effect in making land work more kindly. 

 It answers well with strong clays, rendering them drier, by 

 which they are enabled to be ploughed more early, and to 

 work mellower. 



5. Marl. Of this substance there are four sorts, Rock, 

 Slate, Clay, and Shell marl. The three former are of 

 so heavy a nature, as to be seldom conveyed to any distance ; 

 though useful, when found below a lighter soil, to which they 

 can be applied without incurring much expense. 



As in Lancashire and Cheshire, clay marl is the great source 

 of fertilization, and neither labour nor expense prevents the 

 most vigorous application of it ; it may therefore be proper, to 

 give a general view of the mode of using it adopted in those 

 districts. 



The first object is, the disposition of the pits. These are 

 made where the least land is thereby destroyed ; where they 

 afford the least strength of carriage ; where they require the 

 least draught; where they will occasion the least damage to 

 the lands in future ; and where, if that point can be obtain- 

 ed, it is practicable to lay them dry, when no longer neces- 

 sary ( 231 ). 



The pits are worked by undermining, and loosening on each 

 side large masses, and then by driving long piles in at the top, 

 sometimes with the aid of water, so as to force the mass down. 

 This method is expeditious, but attended with danger to the 

 workmen. 



Marl is generally laid on grass lands, the operation being 

 begun in May or June, and carried on during the summer ; 

 the older the sward the better. The union of the marl and 



