56
THE INTER-RELATIONS OF
of the grains of silicious sand by iron oxide. In the Tunbridge
Wells Sands we find hard ferruginous bands resisting the action of
the weather and so giving varied forms to outstanding rock masses,
as is well seen in the Toad Rock of Rusthall Common.
Excellent illustrations of the chemical action that is constantly
going on in geology are conspicuous in a locality well known to
members of the Essex Field Club, since at Grays in this county may
be seen fine examples of "pipes" in the Chalk, and the eroded top
surface of that formation, all produced by the chemical action of
carbonated surface-water. The destruction of the hard granitic
rocks of the south-west of England by the decomposition of the
felspar of the granite is a familiar illustration of the potency of
atmospheric gases to effect by chemical action great geological
changes.
The preservation by fossilization of vegetable forms by which we
learn the character of the Flora of the past is largely due to chemical
action. Coal plants, having lost their oxygen and nitrogen and much
of their hydrogen, and being reduced to hydro-carbons, are preserved
from further change and utter destruction by this mineralization,
which conserves their original forms and so reveals to us, after an
entombment of countless ages, the beautiful fronds of the ferns and
the symmetrical markings on the Lepidodendrons of the Carboni-
ferous Period. In limestone rocks, however, an entire change takes
place in plant remains, and the whole of the original materials give
place to silica which molecule by molecule replaces the vegetable
matter, while it leaves the plant structure an enduring witness of
the metamorphosis. The formation of stalactite, stalagmite, and
indeed of all mineral deposits in veins or cavities of the rocks,
whether metallic or non-metallic, are due to chemical action, which
is therefore by no means to be disregarded by Field Naturalists.
METEOROLOGY AND BOTANY.
Meteorology and Botany are two essentially Field Naturalists'
subjects, and their intimate connection no one will attempt to dis-
pute. The dependence of plants on climate and weather is com-
plete, and so obvious that illustrations would almost seem to be
out of place when brought before the members of this Society,
which has at its doors as it were the splendid Forest of Epping,
that cannot fail to give a general botanical tone or tendency to the