on the contrary, the shoal is entirely broken up, each fish taking an independent path, and darting from one side of the tank to the other with surprising agility. It was during these active nocturnal movements that the fish struck against the rockwork of the tank and came to an untimely end; this mortality, however, was soon arrested by placing a dim light over their tank, which illuminated the outline of the rockwork just sufficiently to enable them to recognize and avoid it. With this dim light the fish still retained their active habits, and it was noticeable that during these night-hours they were more than ordinarily alert for food, dashing vigorously at any entomostracan or other minute organism that passed through the water. This circumstance would seem to explain why "drift-net" fishing for herrings can be carried on successfully only at night, that being the time when the fish rise to the surface of the water to feed on the innumerable organisms that there abound.
Prof. Mayer on Sound.—Prof. Mayer, of the Stevens Institute of Technology, read at the late meeting of the Academy of Sciences a paper on the "Sensations produced by Concurrent and Rapidly-succeeding Sounds," a synopsis of which appears in the Tribune. The author showed how certain sounds extinguish the sensation of other sounds. The rule appears to be that, while low sounds cannot extinguish high ones, high sounds may obliterate low ones. He had been led to this course of observation by noticing that the click of a noisy clock was, at certain intervals, silenced if a watch was held to the ear. These intervals of silence, he ascertained, occurred when the sharp tick of the watch and the low click of the clock were simultaneous. Then by various and elaborate devices he satisfied himself, not only of the general fact, but as to what balancing of intensities was requisite. Prof. Mayer proceeded to demonstrate the application of the rule to musical sounds. This he made plain to the Academy by means of apparatus producing a certain low note from a wind-instrument simultaneously with the same note several octaves higher and of greater intensity. The high note killed, so to speak, the low one. But, on the other hand, a low note of great intensity was powerless to extinguish a faint high note: the high note utterly refused to be drowned by any volume of the lower sound.
Ancient Condition of Great Salt Lake.—According to Prof. G. K. Gilbert, of Wheeler's Expedition, the Great Salt Lake of Utah anciently had an outlet northward, the overflow being carried to the ocean by the Columbia River. But the Great Salt Lake was then a great inland sea, as is evidenced by the existence of an ancient beach 970 feet higher than the Great Salt Lake of to-day, and 700 feet higher than Sevier Lake. The subsequent changes of level are described as follows by Prof. Gilbert in the American Journal of Science: "From the upper beach the water slowly subsided by desiccation, recording its lingerings in a series of fainter shore-lines. When it had fallen to the level of the divide between the Sevier and Salt Lake Basins, it was separated into two unequal portions. In one of these the evaporation exceeded the inflow from rivers, and the subsidence continued; in the other the inflow exceeded the evaporation, and the surplus was discharged over the divide into the former portion, just as the surplus of Utah Lake is now discharged into Great Salt Lake. In the course of time, as the climate became drier, this overflow ceased, but not until it had carved a channel of some magnitude. This channel is crossed by the old overland stage-route, and is known as the Old River-Bed." It is the opinion of Prof. Gilbert that the humid climate which was marked by this inundation of Utah was preceded by one as arid as the present, and that the humidity was a phenomenon of the Glacial epoch. A fuller statement and discussion of the facts will appear in the forthcoming geological volume of the "Reports of Wheeler's Surveys."
Spontaneous Hypnotism.—A case of spontaneous hypnotism is described by Dr. Bouchut in Les Mondes. A little girl of ten had been apprenticed five months to the business of making waistcoats. One day, after a month of steady but not excessive work, and while sewing a button-hole, she became unconscious and slept for one hour. On awaking, she resumed her work, but with the same result. This hypnotism did
