18 CALCAREOUS MANURES-THEORY. 



" The word loam should be Hmited to soils containincf at least one third 

 of impalpable earthy matter, copioushj effervescing 7vilh acids." [Davy's 

 Agricultural CliemistrT/— Lecture 4.] According to this definition by the 

 most scientific writer and highest authority in chemical agriculture, if we 

 except the small portion of shelly land, there is certainly not an acre of 

 natural loam between the sea-coast of Virginia and the Blue Ridge moun- 

 tains — and very few, if any, even in the limestone region. 



" By loam is meant amj of the earths combined with dcccnjed animal or 

 vegetable matter:'' [Appendix to Agr. Chem. by George Sinclair.] 



"Loam— fat unctuous earth — marl." [Johnsoti's Dictionary, 8vo. ed., 

 and also lValke7'''s.] 



"Loam may be considered a clay of loose or friable consistency, mixed 

 with mica or isinglass, and iron ochre." [^Editor of American Farmer, 

 vol. at, page 320.] 



It seems mo.st proper to class and name soils according to their precZo- 

 minant earthy ingredients, by which term, I mean those ingredients which 

 exert the greatest power, and most strongly mark the character of the soil. 

 The predominant ingredient (in this sense,) is not always the most abun- 

 dant, and frequently is the least. If the most abundant were considered the 

 predominant ingredient, and gave its name to the soil,* then almost every 

 one should be called silicious, as that earth is seldom equalled in quantity 

 by all the others united. If the earthy parts of a soil we^e two thirds 

 silicious, and one third of aluminous earth, the peculiar qualities of the 

 smaller ingredient would predominate over the opposing" qualities of the 

 sand, and the mixture would be a tenacious clay. If the same soil had con- 

 tained only one twentieth part of calcareous earth, that ingredient would 

 have had more marked effects on the soil, than could have been produced 

 by either doubling, or diminishing to half their quantity, the silicious and 

 aluminous earths, which formed the great bulk of the soil. If soils were 

 named according to certain proportions of their ingredients, (as proposed 

 by Davy,t) a correct, though limited analysis of a soil would be required, 

 before its name or character could be given ; and even then the name and 

 character would often disagree. But every farmer can know what are the 

 most marked good or bad qualities of his soils, as shown under tillage, and 

 those qualities can be easily traced to their predominant ingredients. By 

 compounding a (evf terms, various shades of difference may be designated 

 with sufficient precision, A few examples will be sufficient to show how 

 all may be applied : — 



A silicious or sandy soil has such a proportion of silicious earth as to 

 show more of its peculiar properties than those of any other ingredient. It 

 would be more or less objectionable for its looseness, heat, and want of 

 power to retain either moisture or putrescent manure — and not in the least 

 for toughness, liability to become hard after wet ploughing, or any other 

 quality of aluminous earth. 



In like manner, an aluminous or clayey soil would show most strongly 

 the faults of aluminous earth, though much more than half its bulk might 

 be of silicious earth. 



The term loam is not essential to this plan, but it is convenient, as it will 

 prevent the necessity of frequent compounds of other terms. It will be 

 used for all soils formed with such proportions of sand and aluminous earth, 

 as not to be light enough to be called sandy, nor stiff enough for clay soil. 

 Sandy loam and clayey loam would express its two extremes — and loamy 



* Which is the plan of the nomenclature of soils proposed by Rozier. See article 

 " Terres," Cours Complet d'Agriculture, etc. f Agr. Chem. p, 139. 



