SOIL. 



other, though there is eonfiderable difference in this refpeft 

 among different earthy matters, fome being liable to fuftain 

 a great number of different plants in a vigorous ftate of 

 growth, almoft immediately after they become mixed with 

 the foil, while others require to be applied and united for a 

 length of time before they afford fullenance to any kind of 

 vegetable whatever, and even then only yield a fcanty fupply 

 of nourifhment, and that for the fupportofa few particular 

 forts of plants. Where the former forts of materials are 

 abundant, the foils are generally fertile and produftive ; 

 but where the latter prevail, they are mollly iterile and un- 

 friendly to vegetation. Alfo that foils, befides poffeffing the 

 proper earthy matters, muft be embued with other princi- 

 ples, fuch as the aqueous and carbonaceous, and have fuch 

 a confiftence and texture as will properly fupport the plants, 

 as well as fuch proportions of the feveral materials as will 

 admit of their being retained, and applied in fuch quantities 

 as are fuitable for the purpofes of vegetation, according to 

 the differences of climate in refpeft to moifture, and the 

 varieties of fituation in regard to the lands, in order to be 

 rich, fruitful, and produftive, in the different kinds of vege- 

 table crops. It has been ftated likewife, that the bodies or 

 materials, fo far as they are yet known, that have a tendency 

 to leffen the fertility of foils, are the oxyds or calces of par- 

 ticular metals, fome coaly and pyritical matters, acids, and 

 certain heathy vegetable fubftances. But that fome of 

 thefe fubftances, though unfriendly to the growth of vege- 

 tables, when in thefe circumllances, on being blended and 

 united with other materials that enter into the compofition 

 of foils, operate upon them in fuch a manner as to render 

 them more fertile than 'hey would have been without them. 

 Mixtures and impregnations of this nature are conitantly 

 taking place in foils, which cnnnot be eafdy comprehended 

 or aicertaiiied, but which produce great and important ef- 

 fefts and changes in them. From this caufe, foils which are 

 apparently fimilar in every refpedl, on being brought into 

 cultivation, frequently turn out to be effentially different. 

 And It is well known to moft perfens converfant with 

 practical agriculture, that foils in which calcareous matter 

 is predommant, even when they are grown fo poor and ex- 

 haulted as to be almoft incapable of producing any of the 

 other crops commonly cultivated on them, will bear large 

 and repeated crops of one fort of vegetable, that of faint- 

 foin ; and that other foils which are capable of affording 

 the common crops in an abundant manner, cannot be made 

 to produce this. In the fam.e way, fuch calcareous foils as 

 have been cultivated for a great length of time, and are con- 

 fequently much impregnated with manure, afford plentiful 

 crops of barley ; while oat-crops, if attempted to be raifed 

 upon them in fuch a fituation, are weak, puny, and relatively 

 extremely fmall. And, on the contrary, fome primitive 

 foils, not originally containing any calcareous materials, and 

 which, not having been cultivated, cannot be impregnated 

 with manures on firft being broken up, often yield aftonlfh- 

 ing crops of oats, while barley can fcarcely be raifed at all 

 upon them. Thefe and many other fimilar fadts, noticed by 

 cultivators of the foil, fufficiently (hew the effects which 

 even trifling mixtures of certain matters have in altering 

 their qualities, and rendering them more or lefs fertile, as 

 well as more or lefs proper for the growth of particular 

 forts of crops without there being any external appearance 

 of fuch alteration. Further, foils are alfo found to differ 

 greatly from their depths, and the nature of the fub-foils 

 on which they reft. It is ftated as a faft well known by 

 praftical farmers, and which the experience of every day 

 confirms, that even the foils that are conftituted of the molt 



fuitable fubftancf s for the purpofes of vegetation, when only 

 a few inches in depth, and depofited upon beds of cold wet 

 clay, rock, or chalk, are by no means fo fruitful and pro- 

 duftive as thofe which are thicker, though of inferior qua- 

 lity, but refting on a bottom which is more dry and gravelly. 

 The difference of weight and tenacity in the under ftrata of 

 foils, hkewife introduces great variety in regard to their 

 powers and capabilities of raifing and rearing vegetable pro- 

 duftions in the way of crops upon them. 



The variations in the weights of foils are very material, 

 as they (hew in fome meafure the quantities of animal and 

 vegetable matters with which they are impregnated in dif- 

 ferent cafes, the hghter forts being in molt inftances the moft 

 abundant in fuch fubftances. The variations in their powers 

 and properties of diffipating or holding the moifture which 

 they contain are alio very material and important, as they 

 denote, in fome degree, the nature of their compofitions, 

 and their utihty for the growth of different forts of plants 

 as crops. 



The nature and variations of foils, in fo far as they are 

 more or lefs capable of imbibing and retaining the principles 

 of heat, or more cold and raw, or warm in their qualities, 

 which are by no means abfurdities or prejudices, as fome have 

 fuppofed, are highly deferving of the attention of the philo- 

 fophical farmer, as fome foils are evidently much more heated 

 by the effefts of the fun than others, all other circumftances 

 being the fame, while foils brought to the fame ftate of heat 

 cool in different lengths of time, or fome much falter than 

 others. This property, which has hitherto been but little 

 attended to, is thought to be probably of eonfiderable im- 

 portance by the above writer on chemiftry. It is conceived, 

 that in general foils that confift principally of a ftiff white 

 clay are difficultly heated ; and that, being commonly very 

 moift, they retain their heat only for a very (hort time. 

 Chalky foils are fimilar in one particular, which is that of 

 their being heated with difficulty ; but being drier they 

 retain their heat longer, lefs being fuppofed to be confumed 

 in producing the evaporation of their moifture. 



It has been found that a black foil, which contained much 

 foft vegetable matter, was moft heated by the fun and air ; 

 and that the coloured foils, and thofe containing a large 

 proportion of carbonaceous or ferruginous matter, when 

 expofed under equal circumftances to the fun, acquire a 

 much higher temperature than pale-coloured foils. 



In all cafes, when foils are perfeftly dry, thofe that are the 

 moft readily heated by the power of the fun, cool likewife 

 in the moft ready manner ; but fir Humphrey Davy has ex- 

 perimentally afcertained, that the darkell coloured dry foil, 

 or that which contains abundance of animal and vegetable 

 matter ; fubftances which moft facilitate the diminution of 

 temperature, when heated to the fame extent, provided it 

 be within the common limits of the effefts of the fun's heat, 

 will cool more fiowly than a wet pale foil, wholly compofed 

 of earthy matter. He found that a rich black mould, which 

 contained nearly a fourth part of vegetable matter, had its 

 temperature increafed in the courfe of an hour from 65° to 

 88°, by expofure to the fun-fhine ; while a chalk foil was 

 heated only to 69° under the fame circumftances and length 

 of time. But the mould removed into the fhade where the 

 temperature was 62'^, loft, in half an hour, 15° ; while the 

 chalk, under the fame circumftances, had loft only 4°. Far- 

 ther, a brown fertile foil and a cold barren clay were each 

 artificially heated to SS*^, having been previoufly dried : they 

 were then expofed in a temperature of 57° ; in half an hour 

 the dark foil was found to have loft 9" of heat ; the cljy 

 had loft only 6°. An equal portion of the clay contamitig 



moifture, 



