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 millimeter is 1-25th of an inch.
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.