situated on the vertical arm of an angular lever whose other arm is
the key, _t_. When the observer presses the key, the rod, _i_, again
is jerked upward by the spring, _h_. The screw, _o_, tapped into the
rod, _i_, prevents the rod going higher than necessary, by striking a
plate, which also serves as guide for _i_.

To determine the interval between the falling of the ball and pressing
of the key, one has finally to count the waves inscribed by the tuning
fork, which come under the portion of the line inscribed by _s_, which
is bounded by the two breaks produced by the successive movements of
the rod.

To make the glass plate carried by the frame available for more
observations, which plate can be used as a photographic negative, the
frame, T, is adjustable up and down upon the pillars, N. This frame
carries the tuning fork, mercury cup, _n_, and the electro-magnet, M.
The spring, _s_, can also be moved up and down along the rod, i.--_H.
Heele in Zeitschrift fur Instrumentenkunde._

* * * * *




A NEW DISINFECTOR.


The accompanying engravings represent a new disinfecting apparatus
invented by Mr. W.E. Thursfield, M. Inst. C.E., of Victorgasse,
Vienna. The principle on which its action is based is that the