894 - SEA SAND. 



the term, generally, as they did from whom his information was 

 gathered, and in very few cases, if at all, as learned by his own 

 analyses. Therefore, it may well be doubted whether the uncertainty 

 as to the character of marl does not extend very generally to even 

 the most scientific writers on agriculture. 



As some of the foregoing extracts exhibit the use of " marls" 

 (so called) destitute of calcareous earth, so the following shows, 

 under the name of sea sand, a manure which is in its chemical 

 qualities a rich marl (in our sense) or calcareous manure. 



40. " Sea sand. This has been a manure of the district, beyond memory 

 or tradition. There are two species still in use : the one bearing the ordi- 

 nary appearances of sea sand, as found at the mouths of rivers ; namely a 

 compound of the common sand and mud ; the other appears to the eye 

 clean fragments of broken shells without mixture; resembling, in colour 

 and particles, clean-dressed bran of wheat. 



"By analysis, one hundred grains of the former contain about thirty 

 grains of common silicious sea sand, with a few grains of fine silt or mud ; 

 the rest is calcareous earth mixed with the animal matter of marine shells. 



"One hundred grains of the latter contain eighty-five grains of the mat- 

 ter of shells, and fifteen grains of an earthy substance, which resembles, in 

 colour and particles, minute fragments of burnt clay or common red brick, 



"These sands are raised in different parts of Plymouth Sound, or in the 

 harbour; and are carried up the estuaries in barges; and from these on 

 horseback, perhaps five or six miles into the country ; of course at a very 

 great expense, yet without discrimination, by men in general, as to their 

 specific qualities. The shelly kind, no doubt, brought them into repute, 

 and induced landlords to bind their tenants to the use of them ; but with- 

 out specifying the sort and the bargemen, of course, bring such as they 

 can raise and convey at the least labour and expense. It is probable that 

 the specimen first mentioned, is above par, as to quality : I have seen sand 

 of a much cleaner appearance, travelling towards the fields of this quarter 

 of the country ; and near Beddiford, in North Devonshire, I collected a 

 specimen under the operation of "melling" with mould, which contains 

 eighty grains per cent, of clean silicious sand!" Marshall'' s West of Eng- 

 land, vol. i., p. 154. 



It might be inferred from all these proofs of Marshall's know- 

 ledge of calcareous earth constituting the real value of marls, that 

 he could scarcely miss the obvious corollary to that proposition, 

 that the valuable operation of calcareous manures is to render soils 

 calcareous, and that the knowledge of the nature of the manure 

 and the soil would sufficiently indicate when the application of the 

 one to the other is judicious or not. But the following expres- 

 sion of opinion (Marshall's Yorkshire, vol. i., p. 377) is not only 

 strongly opposed to those deductions, but to the general purport 

 of all his truths which I have before quoted. 



41. "Nothing at present but comparative experiments can determino 

 the value of a given lime, to a given soil ; and no man can with common 

 prudence lime any land xipon a large scale, until a moral certainty of im- 

 provement has been established by experience." 



If this be true, then indeed is there no true or known theory ; or 



