52
THE INTER-RELATIONS OF
This combined warning and injunction was given to mankind long
ago by a poet who had no knowledge of Natural History Field Clubs,
the members of which may have a little knowledge of several
branches of Natural History, not only without danger but with very
great advantage. And this is so because they have a sufficient
amount of general knowledge, and of special knowledge in one
department, to enable them to measure correctly their attainments
in a second, or third, or fourth branch of science. Thus they are
preserved from the danger of presumption, which the poet had
doubtless in his mind, and which was a much greater danger in the
days of the education of the few than in these times of a wider
dissemination of knowledge.
There cannot be any member of the Essex Field Club, or indeed
any naturalist whatever, who is unaware of the general connection
that exists amongst the Natural History sciences, and it will there-
fore be quite unnecessary for me here to say anything in insistence of
that great truth, or to do more than give as it were a few reminders
of facts by which this well-known connection is conspicuously dis-
played.
PHYSICS AND GEOLOGY AND METEOROLOGY,
Though the branch of natural knowledge now called Physics is not
usually considered to be one of the sciences included under the term
Natural History, yet the physical forces have had so much to do
with geological results, that the department of science dealing with
them cannot be left out of account by the Field Naturalist. Indeed,
it may be said, that the science of Physics is the basis of all the
Natural History sciences, as the etymology of the word would imply,
for not only the structure of the earth and the character of weather
and climate, but both all vegetable and all animal existence depend
upon, as a foundation, the laws of matter and force, of substance and
energy.
But in Geology and Meteorology these laws force themselves
more obtrusively upon the attention of the student. Dealing first
with Geology, we see the rocks split and rent by their expansion and
contraction consequent upon variation of temperature, upon access
of heat and its withdrawal; or as is commonly said, upon heat
and cold. We further see these split and rent rocks disintegrated
and thrown down, mountain peaks formed and lofty precipices worn
away by the expansion of water when frozen into ice in the rocky
fissures.