584 Indications of Fertility or Barrenness of Soils. 
consequence the arable generally is difficult and expensive to cul- 
tivate. There are exceptions, where the clayey soil is mixed with 
sands, so as to form a loam, and where a considerable depth of 
soil, created by the decomposition of vegetable matter, has accu- 
mulated. In such circumstances the soil is very fertile. 
The pasture-land is generally very good and fertile, pro- 
bably made so by artificial means, and by an accumulation of 
soil on the surface, assisted by a long-continued application of 
manure. The subsoil being clay, this deposit would have been 
as barren as any other of the clay formations, withciut the deep 
covering of mould, or artificial or natural mixture of sand, and 
other ameliorating substances, which are generally found on the 
surface. 
4. Elastic Clay. — This division of the tertiary series is com- 
posed of deposits of sand, clay, rubble, and loam; the latter 
formed by a mixture of the two first mentioned. It is very 
variable in colour, assuming almost all the varied appearances of 
the rainbow. 
Its texture is not uniform, because of the sands and clays 
alternating Avith and succeeding one another, sometimes one 
appearing at the surface, and then the other ; in some places 
forming a wet tenacious soil, very expensive to cultivate, and in 
others a deep porous soil, possessing a considerable degree of 
fertility. In Dorset and Hants the sands of this deposit prevail, 
and there the soil is barren. 
The Secondary System. 
The secondary system is subdivided into seven portions, known 
by the name of formations. 'It extends from the tertiary system 
westward, down to the old red sandstone, where it comes in con- 
tact with the primary system. The formations which compose 
the secondary system are — 1. the Chalk; 2. the Wealden; 3. 
the Oolitic ; 4. the Lias ; 5. the new Red Sandstone ; 6. the 
Carboniferous ; and 7. the old Red Sandstone. 
I. — The Chalk Formation. 
The chalk formation is separated into four subdivisions, which, 
for convenience, we will call deposits: — 1. the Upper Chalk; 
2. the Lower Chalk ; 3. the Gault Clay ; and 4. the Green 
Sand. 
1. The Upper Chalk. — The upper chalk is known by having 
horizontal layers of Hint imbedded in it. The colour is white. 
The chalk-rock is generally near the surface, and covered by a 
very thin coat of mould. The pasture is principally down, and 
fed with sheep, producing but a scanty lierbagc, which, however, 
