MARLING NOT TO MAKE SOIL CALCAREOUS. 



27. The marling of Norfolk county is the most celebrated in 

 England for the great extent of the operation, and the great im- 

 provements thereby made. Yet the following passage from the 

 same writer will clearly show that the ordinary operation called 

 " marling" in Norfolk is entirely different from the chemical action 

 I propose : 



"So convinced" (says Morton, at p. 29), "are the farmers of Norfolk 

 and Suffolk of the value of the clay or chalk marl [both certainly calcare- 

 ous] as an alterative to their sandy surface, that they generally chalk or 

 clay their land once in eight years at least, and sometimes oftener; and by 

 allowing 100 cubic yards to the acre, incur an expense of 50*. [more than 

 $12] per acre, for digging, wheeling, and spreading. It is solely by this 

 process, that the Norfolk sandy soil, which naturally was of the most 

 worthless kind, and produced nothing but heath and bent, for a few starv- 

 ing sheep, is now converted into good sandy loam, which yields large crops 

 of turnips, barley, and wheat." 



Now the first application certainly included the chemical opera- 

 tion which I call marling (or calxing) the soil if it was not before 

 calcareous. If calcareous by nature, even the first artificial appli- 

 cation would have no such chemical action. But much more than 

 half of even the first application, and all of each of the subsequent 

 applications, made every eight years or oftener, in great quantity 

 and at great expense, was merely mechanical in its action, was not 

 rendering the soil calcareous (it being enough so before), and, in 

 short, was in no respect the chemical process which I have defined 

 and recommended, as marling. ,We may infer that in all these 

 later applications, the carbonate of lime in the marl produced no 

 chemical effect, and acted only mechanically, if at all \ and that it 

 was the clay that acted most beneficially, and altogether mechani- 

 cally. 



28. " In Hampshire and Berks, 2880 bushels per acre [of chalk, nearly 

 pure carbonate of lime] are applied with great advantage, at the expense 

 of 42." (Morton on Soils, p. 154.) 



29. There can be no higher authority than Sir Humphrey Davy's, 

 for established scientific opinions, at the time he wrote, as to the 

 characters of soils and mineral manures. His " Lectures on Agri- 

 cultural Chemistry" contain the following passage which with 

 others of similar import remained unaltered in his latest published 

 edition : 



' ' Chalk and marl, or carbonate of lime, will only improve the texture of a 

 soil, or its relation to absorption; it acts merely as one of its earthy ingre- 

 dients" (Agr. Chem. 4th London ed. of 1835, Lecture vii.) 



Of course, neither this illustrious chemist, nor Professor John 

 Davy, who issued, with his notes, this edition of his then deceased 

 brother's great work, could have had any conception of the chemi- 

 cal action of carbonate of lime, when applied in such small quan- 



