Scientific American Supplement, No. 611, September 17, 1887 | Page 8

cars are dependent upon speed of cable. Lost time cannot be made
up except on down grades.
With electricity work done by engine is synchronous with work done
on the track at any time of the day or night, with the loss of 35 per cent.
due to the conversions in each case. In other words, for every horse
power of useful work done on track the engine does 1.54 horse power.
This ratio is constant. It makes no difference whether 1 or 100 horse
power of work is necessary on the track, the engine has but to do 35 per
cent. in excess.

With cable, if 1 horse power of work is all that is required on the track,
the engine may be doing 25 horse power to get that amount there
through the gears and cable. With heavier loads this is somewhat
diminished, but about the very best figure that can be put forth is but 35
per cent. recovery, with 65 per cent. loss--the exact converse of
electricity under heavy loads.--_Street Railway Journal._
* * * * *

ELECTRICAL ALARM FOR PHARMACIES.
[Illustration: FIG. 1.]
To avoid the errors which sometimes occur in a pharmacy or in a
laboratory, where one bottle is taken for another, especially in the case
of those containing highly poisonous or dangerous substances, a simple
arrangement, shown in the cuts, has been proposed. The apparatus, in
principle, is a species of electrical alarm, in circuit with an ordinary
house telegraph line. It consists essentially, as shown in Fig. 1, of a
battery, bell, and pedestal, provided with an electric contact on which
the flask rests. Fig. 2 shows this contact or break piece. On a series of
pedestals thus arranged and intercalated in the same circuit the flasks
containing poisonous or dangerous substances, whose inadvertent
handling might cause trouble, are placed. In removing one of these
flasks the circuit is closed, and the electric bell notifies the pharmacist
of the danger attendant on the use of the substances contained in the
flask referred to, thus guarding against the errors due to carelessness,
and quite too frequent, especially in pharmacies.--_Chronica
Cientifica._
[Illustration: FIG. 2.]
* * * * *

APPARATUS FOR DETERMINING MECHANICALLY THE

REACTION PERIOD OF HEARING.
The following apparatus, constructed after the designs of Dr. Loeb,
assistant in the Physiological Institute at Wurzburg, is for the purpose
of measuring the reaction period of hearing, that is, the period which
elapses between the time when a sound wave affects the auditory nerve
and is thence transferred to the brain, then affecting the consciousness,
and the moment when the motor nerves can be thrown into action by
the will. It is, therefore, necessary to fix both instants--when the sound
is produced and when the observer has, from its warning, received the
impulse so as to press down a key. The great advantage of this
instrument over others adapted for the same end consists in this, that
the determination in its essentials is effected entirely by mechanism,
and, therefore, the graphic results attained by it are free from all
sources of error, which errors other methods always introduce to a
greater or less extent. Thus its results are quite unexceptionable.
[Illustration: REACTION PERIOD OF HEARING.]
The apparatus shown in the cut rests on three feet, two of them
consisting of strong screws, so that by aid of the circular level, l, on the
base plate, it can be adjusted perfectly level. On a little shelf attached to
a square rod, seen on the left of the instrument, rising from the base
plate, and near its top, is a horizontal tube, through which, by a bulb not
shown in the cut, a blast of air can be blown. In front of the other
opening of the tube is a horizontal fork of ebonite, whose arms carry on
the side opposite the tube a metallic ball. Through the arms of the fork
pass the wires of the circuit of an electric battery. These terminate in
two rounded ends, which, when the arms approach each other, are
touched by the metallic ball, so that the latter also closes the metallic
circuit. By the blast of air a wooden wedge contained in the tube is
driven between the arms of the fork, the ball falls from them, and the
electric stream is cut off. The ball drops upon the inclined metallic
plate, p, bounces off it, and is received in a little sack, S. When the
observer hears the ball strike the plate, he presses on the key, t, and the
interval between the two instants, namely, the falling of the ball upon
the plate and the pressing of the key, t, is what is to be mechanically

fixed and measured.
The electric current, which is closed by the