re found at Nassau in Germany in 1864; but as the
phosphate contained a considerable proportion of iron and alumina, they
are not used in this country now, although they are in Germany for
double superphosphate manufacture.

_Bordeaux or French Phosphate._

Similar in quality to Lahn phosphate is that obtained in the
neighbourhood of Bordeaux.

_Algerian Phosphate._

Excellent phosphates are now being sent from Algeria--some cargoes being
as rich as 70 per cent.

_Crust Guanos._

We have already referred to the guanos in the chapter on Guano. They are
also known under the name of Caribbean phosphates, and come from the
West India Islands. The chief kinds are Aruba, Curacao, Sombrero, and
Navassa, the Great Cayman, Redonda, and Alta Vela. Most of them are of
high quality, containing from 60 to 80 per cent of phosphate, and are
thus suited for the manufacture of high-class superphosphates. Some of
them, however, contain a considerable proportion of iron and alumina,
and are not suitable for this purpose. The Redonda and Alta Vela
phosphates consist chiefly of phosphate of alumina.

_Value of Mineral Phosphates as a Manure._

While it is commonly regarded as unadvisable to use mineral phosphates
directly as phosphatic manures, it may well be questioned how far such
an opinion is warranted by actual experience. Professor Jamieson of
Aberdeen, in his interesting and valuable experiments, has drawn
attention to the fact that coprolites in a fine state of division are an
extremely valuable source of phosphoric acid for crops, and are a more
quickly available source than is commonly supposed. Experiments
conducted elsewhere with ground coprolites and other mineral phosphates
corroborate Professor Jamieson's conclusions. The successful use of
Thomas-phosphate has drawn attention to the possibility of profitably
applying undissolved mineral phosphate to the soil; and no doubt the
practice may in future years be increased. At present, however, with the
exception of Thomas-phosphate, mineral phosphates alone are used for
conversion into superphosphate.

FOOTNOTES:

[221] Since the discovery of the Florida deposits of phosphate, the
working of the Canadian mines has been practically abandoned.

[222] See Appendix, p. 381.

[223] These phosphates are now no longer worked.

[224] These deposits were discovered a few years ago; and as they are of
considerable extent and high quality, have entirely revolutioni