tes were very abundant, and that large deposits of them were
found in many parts of the world.

_Coprolites._

Reference may first be made to the so-called coprolites or phosphatic
nodules which have been found in great abundance in the greensand
formation, in the crag of the eastern counties, and in the chalk
formation of the southern counties. These coprolites are rounded
nodules, and are composed of the fossil excrements and remains of
ancient animals. They are found in large quantities in Cambridgeshire,
and were discovered by Dr Buckland many years ago. The history of their
discovery is not a little curious. The manurial properties of
road-scrapings in parts of Cambridgeshire were noticed, and on being
examined were found to be in part composed of phosphate of lime, derived
from phosphatic nodules dug out of the underlying greensand, and used
for the purpose of repairing roads. Professor Henslow first drew
attention to them at a meeting of the British Association held in
Cambridge in 1845, and pointed out that they contained about 60 per cent
of phosphate of lime. They were also found in enormous quantities in
Suffolk, Norfolk, Bedfordshire, and Essex, and were for a long time
largely used in the manufacture of superphosphate, but of late years
have not been used to anything like the same extent, owing to the fact
that there are richer and cheaper sources of phosphate of lime
available. In 1887 about 20,000 tons of coprolites were raised. The
richest were those obtained in Cambridge, while those got from
Bedfordshire were about the poorest. Deposits have also been found in
France and other countries. The average amount of phosphate of lime in
English coprolites is between 50 and 60 per cent, while the French
contain about 45 per cent.

_Canadian Apatite or Phosphorite._

We have already referred in Chapter V. to large deposits of apatite or
phosphorite found in Canada. The Canadian mines commenced to be worked
about fifteen years ago, and the output now amounts to nearly 25,000
tons per annum.[221] A portion of this goes to the United States; the
rest, amounting to about 20,000 tons, being shipped to England, whence
it is again exported to Hamburg and other places.[222] It contains from
70 to 80 per cent of phosphate. Deposits are also found at Estremadura
in Spain, and in Norway.

_Estremadura or Spanish Phosphates._

Large deposits of phosphate have long been known to exist at Estremadura
in Spain,