py also found chalk-like coral
limestones containing 95 p.c. of carbonate of lime in the Solomon Islands.

The absence of _Globigerinae_ is a local phenomenon. They are quite absent
in the Arafura Sea, and no _Globigerina_-ooze was found in any of the
enclosed seas of the Pacific, but with these exceptions the _Globigerinae_
"are really found all over the bottom of the ocean." (Murray on Oceanic
Deposits--_Proceedings of Royal Society_, Vol. XXIV., p. 523.)

The above analysis shows a far closer resemblance to chalk than that of the
_Globigerina_-ooze of the Atlantic, four specimens of which given by Sir W.
Thomson (_Voyage of the Challenger_ Vol. II. Appendix, pp. 374-376, Nos. 9,
10, 11 and 12) from the mid-Atlantic, show the following proportions:--

Carbonate of Lime 43.93 to 79.17 per cent.
Carbonate of Magnesia 1.40 to 2.58 ,,
Alumina and Oxide of Iron 6.00? to 32.98 ,,
Silica 4.60 to 11.23 ,,

In addition to the above there is a quantity of insoluble residue
consisting of small particles of sanidine, augite, hornblende, and
magnetite, supposed to be the product of volcanic dust or ashes carried
either in the air or by ocean currents. This volcanic matter amounts to
from 4.60 to 8.33 per cent. of the _Globigerina_-ooze of the mid-Atlantic,
where it seems to be always present; and the small proportion of similar
matter in true chalk is another proof that its origin is different, and
that it was deposited far more rapidly than the oceanic ooze.

The following analysis of chalk by Mr. D. Forbes will show the difference
between the two formations:--

Grey Chalk, White Chalk,
_Folkestone_. _Shoreham_.

Carbonate of Lime 94.09 98.40
Carbonate of Magnesia 0.31 0.08
Alumina and Phosphoric Acid a trace 0.42
Chloride of Sodium 1.29 --
Insoluble debris 3.61 1.10

(From _Quarterly Journal of the Geological Society_, Vol. XXVII.)

The large proportion of carbonate of lime, and the very small quantity of
silica, alumina, and insoluble _debris_, at once distinguish true chalk
from the _Globigerina_-ooze of the deep ocean bed.

[24] Notes on Reticularian Rhizopoda; in _Microscopical Journal_, Vol.
XIX., New Series, p. 84.

[25] _Proceedings of the Royal Soci