and which contain a fair proportion of loamy 
clay and vegetable matter, absorb large supplies 
of moisture from the atmosphere in dry weather, 
and at the same time do not become cohesive or 
pultaceous after rains. The following table from 
Schiibler shows the quantity of moisture absorb- 
|| ed from the atmosphere, in respectively 12, 24, 
| 48, and 72 hours, by 1,000 grains of each of 13 
|| substances, spread on a surface of .50 square 
| inches :— 
Inl2 In 24 In 48 In 72 
Substances. hours. hours. hours. hours. 
Silicious sand. ‘ 0 ) 0 0 
Caleareous sand. he aad 3 3 3 
Gypsum powder 6 1 1 ] 1 
Sandy clay. f ok 26 28 28 
Loamy clay. 25 30 34 30 
Stiff clay 30 36 40 4] 
Grey pure clay . : 37 42 48 49 
Fine carbonate of lime 26 3l 385 35 
Fine carbonate of magnesia 69 76 80 82 
Humus 80 OH MNO) LARD 
Garden mould 35 45 50 52 
Arable soil 16 22 23 23 
Slaty marl 24 29 32 33 
The relative geological characters of soils, or 
those which involve their connexion with the 
| agencies and influences of the subsoil, have re- 
_ ference partly to their original constitution, 
| partly to the local facilities for improving them, 
and partly or even chiefly to the circulation of 
moisture through them or to the circumstances 
_ of their drainage.—Soils which rest directly upon 
solid rock, whether on hill or plain, generally 
owe their mineral constituents to the disintegra- 
tions immediately below and around them; so 
that their general nature and value, in so far as 
these depend upon their mere original composi- 
| tion, may be accurately estimated by reference 
to the geognostic formations on which they lie. 
Soils formed directly on granite, quartz, ser- 
pentine, and generally on silicious primitive 
| rocks are barren; those formed directly on mag- 
nesian limestone are bad ; those formed directly 
on all tolerably pure calcareous limestones are 
productive; those formed directly on the shales 
and sandstones intermediate between the tran- 
sition and the tertiary rocks, are bad, indifferent, 
or good, according to the predominance of silica 
in the rocks or to the degrees of its intermixture 
with alumina and lime; and those formed di- 
rectly on the basalts, greenstones, and porphy- 
ries of the trap rocks are generally fertile. See 
also some statements in the article Barren Sots. 
—Soils which rest upon earthy strata may, when 
properly worked by intelligent and skilful hus- 
_bandry, owe more of their practical worth or 
worthlessness to the depth and the nature of 
these strata than to their own composition 
| When the under-strata are deep and porous, no 
expense requires to be incurred for forming and 
maintaining a system of artificial subsoil drain- 
age ; when they are comparatively rich in or- 
ganic matter and in alkalies and salts, they afford 
|| a ready mine for the deepening or renovating 
or enriching of the soil by the simple process of 
trenching or trench-ploughing ; and when they 
contain a supply of any necessary ingredient in 
which the soil is deficient, or which would tend 
to improve it, as of clay beneath sand or of lime- 
stone gravel beneath peat, they offer the amplest 
facility for effecting improvement by textural 
intermixture. But, on the other hand, when the 
under-strata are stubbornly retentive, a system 
of artificial subsoil drainage is essential to ferti- 
lity; when they are poor in organic matter and 
in salts, and especially when they contain noxious 
metallic oxides, they would injure the soil, and 
not improve it, by being trenched up; when 
they are minerally the same in nature as the 
soil, they offer little or nothing for textural im- 
provement; and when they are porous and lie 
very near the surface, they both starve all deep- 
rooting plants, and occasion a rapid exhaustion 
of internal moisture at a time of drought.—The 
strata immediately beneath the soil, whether 
they be solid or earthy, differ widely in their 
effects upon the circulation of air and moisture, 
or upon all those properties of soil which are de- 
pendent on drainage. 
The mutational characters of soils might be so 
comprehensively defined as to comprise all sorts . 
of changes whatever which take place in soils 
both naturally from the agencies of meteorology, 
chemistry, and vegetation, and artificially from 
the operations of georgy, tillage, manuring, and 
cropping ; but they are understood here in so re- 
stricted a sense as to comprise only the changes 
and fluctuations which result from successions of 
vegetable growth, partly in a natural way, but 
chiefly in courses of cropping ; and even as thus 
limited in meaning, they present to the farmer 
a great and diversified and eminently important 
subject of study,—no less, in fact, than the whole 
question of constant mutations in composition 
and fertility arising, on the one hand, from the 
withdrawal of ingredients by unreturned weeds, 
crops, and cattle,.and, on the other, from the 
adding of ingredients through the medium of 
fallowing and of feeding-off and in the form of 
manure. The subject, however, belongs rather 
to the chapter of current cultivation than to the 
chapter of soils, and has already been pretty 
fully discussed, though in an incidental way, in 
the articles Manure and Rotation or Crops; 
and it is introduced here principally for the ke 
of reminding intelligent farmers that, in the pre- 
sent advanced state of agricultural science, they 
may enjoy the luxury and reap the benefit of 
keeping an estimate-account of the fluctuating 
powers of every field, so as to show at a glance 
the balance between fertility withdrawn by crops 
and stock and fertility imparted by ameliorations 
and manurings,—and of presenting to them the © 
following table, by the help of which, along with 
that of the analyses of the several manures given 
in their proper places, they may see the prin- 
ciples on which such an account must be framed: . 
