Page:Popular Science Monthly Volume 12.djvu/263

Rh more complex problems, as will be seen from the following account of their labors, which we take from the English Mechanic. In these experiments by pressure of a brush saturated with a concentrated solution of a savory substance on the tongue, an electric circuit was closed, which was only opened by the person when he made a signal "on first perceiving the taste. The time during which the current flowed was marked by a rotating cylinder, and represented the "reaction-time" of a given taste. First, the "reaction-time" of four different substances was ascertained. This experiment was then so modified that not merely the sensation of taste had to be answered to, but the tongue of the person was touched now with water, now with a savory solution, without his knowing beforehand which was to be applied; he had to decide which had touched his tongue, and gave the signal only when it was the savory matter. In a final series of experiments there were always two savory substances used: when the person perceived the one, he gave the signal with one hand; when he perceived the other, with the other hand. Here the person had not only to perceive the sensation, but to distinguish the one taste from the other, and then to make the right choice of the hand to give the signal. The results are stated in the table below, where the first vertical series gives the names of the savory substances; the second, the time in seconds between the application of the substance and giving of the signal; the third, the reaction-time when the savory substance was applied interchangeably with water, and must be distinguished from this; the fourth, fifth, sixth, and seventh, the reaction-time in comparison with common salt, acid, sugar, and quinine, respectively:

"If we take as a basis," say the authors, "the reaction-times when the tongue was touched with a savory substance alone, and compare therewith the reaction-times which were obtained in the experiments whether with water, or with another savory substance, we find that the following law generally holds: If we experiment with distilled water and a savory substance, or interchangeably with two savory substances on the tongue-tip, then the time of recognition of the one (in experiments with water), or of the two (in experiments with savory substances), is longer, the longer the reaction time of one of the savory substances on simple application." The converse of this law, however (which is only in general valid), does not hold good.

An Underground Pneumatic Clock-Regulator.—The inhabitants of modern cities who are accustomed to receive their supply of water and illuminating gas through pipes laid under the streets, and who are prepared to welcome the introduction of a system of steam-heating on a large scale, will next "get the time of day" from underground pipes. A plan of regulating clocks by means of compressed air has been devised by an Austrian engineer named Mayrhofer. Its principle will be understood from the following description, which we take from the Boston Journal of Chemistry: In the first place, tubes are laid to convey compressed air from a central station, in which is the "master-clock." A simple contrivance, connected with the tubes and the clock, lets off a puff of air every minute or half-minute, and the fingers of all the clocks in the system are in that manner pushed forward with unerring accuracy, in accordance with the time indicated by the standard timepieces in the observatory, so that exact uniformity can be maintained without difficulty in the time shown on any number of dials. The weather has no effect on the air, so far as the working of the pneumatic clocks is concerned, and, be it hot or be it cold, the little valve lets off its puff of air, and the clocks go accurately, in defiance of atmospherical influences. A small yearly charge is made for the clocks, and there is no further expense or trouble. The system has been in operation in Vienna for nearly four months, and has worked without a solitary hitch, so that the people are beginning to realize the idea that time can be "laid on" in then houses as readily as either water or gas.