The elevation of our planet's temperature is
therefore a direct consequence of the existence of aqueous vapor in our
air. Flimsy as that garment may appear, were it removed terrestrial life
would probably perish through the consequent refrigeration.
I have thus endeavored to give some account of a recent incursion into
that ultra-sensible world mentioned at the outset of this paper. Invited
by my publishers, with whom I have now worked in harmony for a period of
twenty years, to send some contribution to the first number of their new
Magazine, I could not refuse them this proof of my good will.
J. TYNDALL
Alp Lusgen, September 4, 1882
* * * * *
The German empire has now about 34,000,000 acres of
forest, valued at $400,000,000, and appropriates $500,000
even year to increase and maintain the growth of trees.
* * * * *
APPARATUS FOR MEASURING ELECTRICITY AT THE UPPER SCHOOL OF TELEGRAPHY.
_Electro Tuning Forks and their Uses._--On a former occasion I described
an instrument to which, in 1873, I gave the name _Electro-Tuning Fork_,
and which is nothing else than a tuning fork whose motion is kept up
electrically in such a way as to last indefinitely, provided that the
elements of the pile are renewed gradually, and that from time to time
the metallic contact is changed, which causes, at every oscillation, the
current to pass from the pile into the magnet, which keeps up the
vibration.
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