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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.]

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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