h has now been many years on the wane', but has recently been
revived),[620] Welsh, Red Polled, Jerseys, Guernseys, Kerry and
Dexter-Kerry.

The increased variety of sheep was also striking; Leicesters,
Cotswolds, Lincolns, Oxford Downs, Shropshires, Southdowns, Hampshire
Downs, Suffolks, Border Leicesters, Clun Forest, and Welsh Mountain.

Pigs were divided into Large, Middle, and Small white Berkshires, any
other black breed, and Tamworths.

Altogether the total number of stock exhibited was 1,858, and the
number of implements was 5,430.

In 1840 appeared Liebig's _Chemistry in its Application to Agriculture
and Physiology_, tracing the relations between the nutrition of plants
and the composition of the soil, a book which was received with
enthusiasm, and completely changed the attitude which agriculturists
generally had maintained towards chemistry; one of contempt, founded
on ignorance.

But, as Mr. Prothero has said,[621] 'if the new agriculture was born
in the laboratory of Glissen, it grew into strength at the
experimental station of Rothamsted.' There, for more than half a
century, Lawes and Gilbert conducted experiments, of vast benefit to
agriculture, in the objects, method, and effect of manuring; the
scientific bases for the rotation of crops, and the results of various
foods on animals in the production of meat, milk, and manure.

The use of artificial manures now spread rapidly; bones, used long
before uncrushed, are said to have been first crushed in 1772, and
their value was realized by Coke of Holkham, but for long they were
crushed by hammer or horse mill, and their use was consequently
limited. Then iron rollers worked by steam ground them cheaply and
effectively, and their use soon spread, though it was not till about
1840 that it can be said to have become general. Its effects were
often described as wonderful. In Cheshire, cheese-making had
exhausted the soil, and it was said that by boning and draining an
additional cow could be kept for every 4 acres, and tenants readily
paid 7 per cent. to their landlords for expenditure in bone manure.
Its use had indeed raised many struggling farmers to comparative
independence.[622] A very large quantity of the bones used came from
South America.[623] Porter also noticed that 'since 1840 an extensive
trade has been carried on in an article called Guano', the guana of
Davy, 'from the islands of the Pacific and off the coast of Africa'.
Nitrate of soda