382 ERRORS or MODERN AUTHORS. 



more abundant, more finely reduced, and consequently more fit for 

 both immediate and durable effects) are considered as less effica- 

 cious than solid sea shells, and inferior to sea sand. All these 

 substances, besides whatever service their salts may render, are pre- 

 cisely the same kind of calcareous manure, as our beds of fossil 

 shells furnish in a different form. Yet neither here nor elsewhere, 

 does the author intimate that these manures and marl have similar 

 powers for improving soils. 



The foregoing quotations show what opinions have been expressed 

 by English writers of reputation, and what opinion would thence 

 necessarily be formed by a general reader of these and other agri- 

 cultural works, of the nature of what is called marl in England, as 

 well as what is so named in this part of our country. I do not 

 mean that other authors have not thought more correctly, and 

 sometimes expressed themselves with precision on this subject. 

 Mineralogists define marl to be a calcareous clay ; and in this cor- 

 rect sense, the term is used by Davy, and other chemical agricul- 

 turists. Such authors as Young and Sinclair also could not have 

 been ignorant of the true composition of marl ; yet even they have 

 used so little precision or clearness, when speaking of the effects of 

 marling, that their statements (however correct they may be in the 

 sense they intended them) convey no exact information, and have 

 not served to remove the erroneous impressions made by the great 

 body of their predecessors. Knowing as Young did [see above, 

 11] the confusion in which this subject was involved, it was the 

 more incumbent on him to be guarded in his use of terms so gene- 

 rally misapplied. Yet considering his practical and scientific 

 knowledge as an agriculturist, his extensive personal observations, 

 and the quantity of matter he has published on soils and calcareous 

 manures, his omissions are more remarkable than those of any 

 other writer. In such of his works as I have met with, though 

 full of strong recommendations of marling, in no case does he state 

 the composition of the soil (as respects its calcareous ingredient), 

 or the proportion added by the operation ; and generally notices 

 neither, as if he viewed marling just in the same loose and incor- 

 rect manner as most others have done. These charges are supported 

 by the following extracts and references. 



17. Young's Farmer's Calendar, 10th London edition, page 

 40. On marling. Through nearly four pages this practice is 

 strongly recommended but the manures spoken of, are regularly 

 called " marl or clay," and their application, " marling or claying." 

 Mr. Rodwell's account of his practice (which I before referred to, 

 p. Ill,) is inserted at length. On leased land he " clayed or marled" 

 eight hundred and twenty acres with one hundred and forty thou- 

 sand loads, and at a cost of four thousand nine hundred and fifty- 

 eight pounds and the business is stated to have been attended 



