ther the rings be
large or small, we ordinarily find them occurring in the same specimens
in groups of larger and smaller. In one of my Helmsdale specimens,
indicative generally of rapid growth, there are four contiguous annual
rings, which measure in all an inch and two twelfths across, while the
four contiguous rings immediately beside them measure only half an inch.
"If, at the present day," says a distinguished fossil botanist, "a warm
and moist summer produces a broader annual layer than a cold and dry
one, and if fossil plants exhibit such appearances as we refer in recent
plants to a diversity of summers, then it is reasonable to suppose that
a similar diversity formerly prevailed." The same reasoning is of course
as applicable to _groups_ of annual layers as to _single_ annual layers;
and may we not venture to infer from the almost invariable occurrence of
such groups in the woods of this ancient system, that that
ill-understood law of the weather which gives us in irregular
succession groups of colder and warmer seasons, and whose operation, as
Bacon tells us, was first remarked in the provinces of the Netherlands,
was as certainly in existence during the ages of the Oolite as at the
present time?

[Illustration: Fig. 130.

CONIFERS?]

[Illustration: Fig. 131.

CONIFER TWIGS.]

Twigs which exhibit the foliage of these ancient conifers seem to be
less rare in our Scotch deposits than in those of England of the same
age. My collection contains fossil sprigs, with the slim needle-like
leaves attached, of what seem to be from six to seven different
species; and it is worthy of notice, that they resemble in the group
rather the coniferae of the southern than those of the northern
hemisphere. One sprig in my collection seems scarcely distinguishable
from that of the recent _Altingia excelsa_; another, from that of the
recent _Altingia cunninghami_. Lindley and Hutton figure in their fossil
flora a minute branch of _Dacrydium cupressinum_, in order to show how
nearly the twigs of a large tree, from fifty to a hundred feet high, may
resemble some of the "fossils referable to Lycopodiaceae." More than one
of the Oolitic twigs in my collection are of a resembling character, and
may have belonged either to cone-bearing trees or to club mosses.
Respecting, however, the real character of at least one of the
specimens,--a minute branch from the Lias of Eathie, with the leaflets
attached,--there can be no mistake. The