ON MANURES. IO5 



When the earth which is required to be added is to be found 

 in the subsoil, then, indeed, if it be not at too great a depth, it 

 may perhaps be dug, at those seasons in which labour is cheap, 

 at a moderate expense ; but those instances are rare, and the 

 charge of cartage from a distance must prevent it from being 

 undertaken by any man, although the owner of the land, who 

 is not possessed of large disposable capital, or by any tenant 

 who cannot secure the return of the outlay within the currency 

 of his lease. Composts, however, may be very advantageously 

 formed in the manner we have stated — by a mixture of lime 

 with the earth on which it is to be laid. 



CHAPTER V. 



MINERAL MANURES CONTINUED. MARL. 



Marl is a compound calcareous earth found in most parts 

 of the world, and has been extensively used throughout this 

 kingdom, where it is supposed to have been known to hus- 

 bandmen at a very early period of our history. There are, 

 indeed, leases on record, granted in the reigns of Edward I. 

 and II., which compel the tenants to make use of it; but, 

 though still employed, it has been in a great degree super- 

 seded by the more recent introduction of lime, of the pro- 

 perties of which it in some measure partakes. The term 

 denoting it was formerly used in a very vague sense, for it is 

 a substance consisting of various materials, and it has conse- 

 quently happened, that what has been supposed to apply to 

 one species, did not hold good when affirmed of another. 

 Although principally deemed valuable on account of the calca- 

 reous matter which it usually contains, still its composition 

 differs so essentially, that its influence as manure is but im- 

 perfectly understood ; yet theoretic writings abound in gene- 

 ral directions for its use, which are frequently found not to ' 

 answer in practice, for their rules are drawn either from state- 

 ments which have been made of the effect of its application on 

 particular soils, or from analysis of its qualities, which, as 

 these vary in innumerable instances, frequently lead farmers 

 astray. Its real value can, therefore, be only ascertained 



