376 OF THE USE OF CHALK AS A MANURE. 



But to these and other effects I shall have occasion to draw your at- 

 tention more particularly in a subsequent part of the present lecture. 



§ 7. Of the use of chalk as a manure. 



Chalk is another form of carbonate of lime which occurs very abun- 

 dantly in nature, and which, from its softness, has in many parts of 

 England been extensively applied to the land in an unburned state. 



The practice of chalking prevails more or less extensively in all 

 that part of England (Lec."XI., § 8,) over which the chalk formation 

 extends. It is usually dug up from pits towards the close of the au- 

 tumn or beginning of winter, when full of water, and laid upon the 

 land in heaps. During the winter's frost the lumps of chalk fall to 

 pieces, and are readily spread over the fields in spring. The quantity 

 laid on varies with the quality of the soil and of the chalk itself, and 

 with the more or less perfect crumbling it undergoes during the season 

 of winter, and with the purpose it is intended to serve. It gives tena- 

 city and closeness to gravelly soils,* opens and imparts freeness to stiff 

 clays, and adds firmness to such as are of a sandy nature. 



If a physical improvement of this kind be required, it is laid on at 

 the rate of from 400 to 1000 bushels an acre. But some chalks con- 

 tain much more clay than others, and are employed, therefore, in small- 

 er proportions. 



For the improvement of coarse, sour, marshy pasture, it is applied at 

 the rate of I'SO to 250 bushels an acre, and speedily brings up a sweet 

 and delicate herbage. It is also said to root out sorrel from lands that 

 are infested with this plant. 



These effects are precisely such as usually follow from the applica- 

 tion of marl, and, like marl, the repetition of chalk exhausts the land, if 

 manure be not afterwards added to it in sufficient quantity. 



But tlie chalking of the Southern Downs and of the Wolds of Lin- 

 colnshire and Yorkshire would appear to differ in some respects from 

 ordinary marling. On the thin soils immediately resting upon the 

 chalk, experience has shown that repeated dressings of chalk recently 

 dug up, may be applied with much benefit. To a stranger, also, it ap- 

 pears singular that an admixture of that chalk which lies immediately 

 beneath the soil is not productive of the same advantage. Even the 

 chalk of an entire district is, in some cases, rejected by the farmer, 

 and he will rather bring another variety from a considerable distance, 

 than incur the less expense of laying on his land that which is met 

 with on his own or on his neighbors' farms. Thus the Suffolk farmers 

 prefer the chalk of Kent to lay on their lands, and are at the cost of 

 bringing it across the estuary of the Thames, though chalk rocks lie al- 

 most everywhere around and beneath them. 



The cause of the diversities which thus present themselves in the 

 practice of experienced agriculturists, partly at least, is to be sought for 

 in the qualities of the different varieties of chalk employed. Careful 

 analyses have not yet shown in what respects these chalks differ in che- 

 mical constitution, and until this is ascertained we must remain in 



* Mr. Gawler, North Hampshire, states that a gravel thus stiflFened, instead of 12 to 16 

 bushels of wheat, yielded afterwards 24 to 30 bu&lieis.— British Husbandry , i., p. 280. 



