386 



THE SOUTHERN PLANTER. 



would then come under the description of 

 highly fertile soils. 



Intimately connected with the preced- 

 ing property, is the power of soils absorb- 

 ing fertilizing gases from the atmosphere. 

 Carbonic acid and ammonia, with which 

 we are more especially concerned, and 

 which both exist in small proportions in. 

 the atmosphere, are both absorbed by the 

 various soils in very different degrees. 

 Generally speaking, those soils which ab- 

 sorb a larger amount of moisture from the 

 air than others, are also the better absorb- 

 ers for carbonic acid and ammonia. This 

 property, though dependent in a great 

 measure on the porosity or the state of 

 division of the various constituent parts 

 of the soil, is nevertheless still more in- 

 timately connected with its chemical con- 

 stitution, as we shall presently show. 

 Good clay-loams and arable soils, contain- 

 ing a certain amount of vegetable and an- 

 imal remains, possess it in a considerable 

 degree ; on the contrary, very sandy soils 

 scarcely absorb any appreciable quantity 

 of the fertilizing gases which have just 

 been mentioned. 



Another important property, which in- 

 fluences the agricultural capabilities of 

 soils, is their power of holding water. 

 Some soils will drink in and retain a much, 

 larger proportion of rain falling upon' 

 them than others, before the rain perco- 

 lates into the subsoil ; and it is evident 

 that in dry climates this property must 

 render a soil more valuable. In districts 

 visited by frequent and heavy showers 

 of rain, on the contrary, it is not desirable 

 that a soil should possess t his property in 

 any large degree. Clay and peaty soils, 

 it is well known, are capable of contain- 

 ing a very much larger amount of water 

 than sandy soils ; and as in the evapora- 

 tion of the larger quantity of water con- 

 tained in the former, a more considerable 

 amount of heat is expended to change the 

 water into vapour, we are taught at once 

 the reason why clay soils are colder than 

 sandy ones. If water is poured on 

 weighed quantities of soils of different 

 descriptions, a certain amount disappears 

 in each instance ; and if the careful ad- 

 dition of water is stopped when the first 

 drop passes through the mass of the soils, 

 and the latter are now weighed again, 

 great differences will be found in the 

 quantities of water which are contained 



in each sample of soil. Thus it has been 

 found, that from 100 lbs. of dry soil, wa- 

 ter will begin to drop, if it be a 



Quartz sand, when it has absorbed 25 lbs. 



Calcareous sand, " 29 " 



Loamy soil, " ■ 40 f 



English chalk, " 45 « 



Clay-loam, " 50 " 



Pure clay, " 70 " 



Again, those soils which hold the larg- 

 est amount of water, also retain it with 

 the greatest pertinacity — another proper- 

 ty which accounts partially for the dissimi- 

 larity in the fertilizing characters of soils. 

 Then again, in the relation of different 

 soils to heat, we observe great differences. 

 Thus, dark-colored soils will absorb a 

 greater amount of heat from the sun's 

 rays than light-colored ones : but the lat- 

 ter will retain the heat they have absorb- 

 ed much longer than the former. If we 

 further take into consideration the great 

 differences in the firmness or adhesive 

 power of various soils, their relative 

 depth, position, and many other circum- 

 stances, it will become apparent that 

 many circumstances besides their chemi- 

 cal composition exercise a more or less 

 considerable influence on their natural 

 productive power.- 



The study of the characters of soils, 

 it appears to us, has hitherto been prose- 

 cuted too much in a one-sided direction. 

 On the one hand, the mere existence of 

 a certain number of chemical constitu- 

 ents has been deemed sufficient to ac- 

 count for all the agricultural peculiarities 

 of soils ; and, on the other hand, their 

 physical properties have been too much 

 considered, independently of their chemi- 

 cal composition. That an intimate con- 

 nection exists between the physical pro- 

 perties and the chemical composition of 

 soils, we have already had occasion to re- 

 mark, but unfortunately this relation has 

 not always been recognized ; we have 

 hitherto been too much in the habit of 

 looking upon the soil as dead matter, 

 and have, consequently, given but little 

 attention to the various functions which » 

 the different constituents, in their various 

 combinations, are calculated to perform 

 in relation to vegetable life ; in short, we 

 have too little endeavored to study the 

 physiology of soils. It affords us, there- 

 fore, particular pleasure to direct the 



