exterior outline in the stone.

[Illustration: Fig. 152.]

One or two general remarks, in conclusion, on the Oolite flora of
Scotland may be permitted me by the Association. In its aspect as a
whole it greatly resembles the Oolite flora of Virginia, though
separated in space from the locality in which the latter occurs by a
distance of nearly four thousand miles. There are several species of
plants common to both, such as _Equisetum columnare_, _Calamites
arenaceus_, _Pecopteris Whitbiensis_, _Lycopodites uncifolius_, and
apparently _Taeniopteris magnifolia_; both, too, manifest the great
abundance in which they were developed of old by the beds of coal into
which their remains have been converted. The coal of the Virginia Oolite
has been profitably wrought for many years: it is stated by Sir Charles
Lyell, who carefully examined the deposit, and has given as the results
of his observation in his second series of Travels in the United States,
that the annual quantity taken from the Oolitic pits by Philadelphia
alone amounted to ten thousand tons; and though, on the other hand, the
Sutherlandshire deposit has never been profitably wrought, it has been
at least wrought more extensively than any other in the British Oolite.
The seam of Brora, varying from three feet three to three feet eight
inches in thickness, furnished, says Sir Roderick Murchison, between the
years 1814 and 1826, no less than seventy thousand tons of coal. Such is
its extent, too, that nearly thirty miles from the pit's mouth (in
Ross-shire under the Northern Sutor) I have found it still existing,
though in diminished proportions, as a decided coal seam, which it must
have taken no small amount of vegetable matter to form. And almost on
the other side of the world, nearly five thousand miles from the
Sutherland beds, and more than eight thousand miles from the Carolina
ones, the same Oolitic flora again appears, associated with beds of
coal. At Nagpur in Central India the Oolitic Sandstones abound in simple
fronded ferns, such us Taeniopteris and Glossopteris, and has its
Zamites, its coniferous leaves, and its equisetaceae.

Compared with existing floras, that of our Scottish Oolite seems to have
most nearly resembled the flora of New Zealand,--a flora remarkable for
the great abundance of its ferns, and its vast forests of coniferous
trees, that retain at all seasons their coverings of acicular spiky
leaves. It is to this flora that _Dacrydium cu