110 THE NAME OP MARL MISAPPLIED. 



[Nevertheless, much, valuable information may be obtained from 

 these same English works, on calcareous manure, or on marl (in the 



sand-stone" formation of England is largely composed of a true (calcare- 

 ous) "red marl." The soil in question was probably a red clay, but, as I 

 should suppose, containing not a particle of calcareous earth and cer- 

 ^aiuly having no quality in common with any marl, true or false, or agree- 

 ing with any of the different understandings of what marl is, in texture or 

 composition. 



According to scientific definition, marl is composed of carbonate of lime 

 and fine clay. When taken moist from its bed, such marl is not ductile or 

 plastic, like ordinary clay ; and is broken more easily than bent. It is 

 cut by a knife to a smooth surface, having an unctuous or soapy feel. When 

 a lump has been dried, and is then put into water, it speedily crumbles to 

 powder, or into thin lamime. Puvis (in his " Essai sur la Marne"), con- 

 siders the clay and carbonate of lime in marl to be chemically combined 

 which opinion seems well founded. He also supposes marl to be generally, 

 if not universally, of fresh-water formation as shown by the shells con- 

 tained. 



The term marl may be considered as understood in four principal signi- 

 fications, and two of these running into numerous provincial varieties. 

 With all the precision and care in defining that can be used, it will not be 

 possible for me to avoid using the term sometimes in the different senses in 

 which it is used by other authorities to whom I may refer, or whose opinions 

 may be quoted. Therefore, it will serve for better understanding and 

 greater clearness, to state, in general terms, all the different meanings ap- 

 plied to the term marl, by different classes. 



1. The definition of marl by mineralogists, and men of science, is the 

 most exact and most restricted in application a calcareous clay of pecu- 

 liar texture and physical qualities, as described more at full above, and 

 elsewhere in this work. 



2. The most extended sense in which I shall use it in reference to its 

 fertilizing operation, (calxing), to embrace every kind of substance of earthy 

 texture, containing carbonate of lime in useful quantity to serve as manure, 

 and that being the principal manuring ingredient. 



3. The sense in which it is understood by modern British agricultural 

 authors which is the mineralogical marl, but also embraces other earths 

 used for the calcareous contents. 



4. All the provincial applications of the term in different regions as to 

 fine clay (in England) fossil shells, in lower Virginia calcareous tufa, 

 or travertine, in our mountain region and non-calcareous green-sand, 

 in New Jersey, &c. : In short, to any kind of earth that experience has 

 proved, or that ignorance has supposed, to be useful as manure. 



The operation called "marling" in England is even less like what is 

 known by the same name here, than are the different substances used un- 

 der that name. That which I have done, and advise, and call marling (in 

 conformity to our provincial and incorrect name given to the substanco 

 used), is, as above stated, the application of calcareous earth of any kind, 

 or from any source, to soils deficient in that ingredient and also, in quan- 

 tities no greater than will serve to produce the desired chemical change in 

 each particular soil. This required proportion of carbonate of lime is 

 rarely more than will make one per cent, of the soil for its ploughed depth ; 

 and generally less than half that quantity is enough for profit and for 

 safety. Hence, according to the strength of the manure and the condi- 

 tion of the soil, the usual applications lie between the extremes of 100 and 



