The increase in height of the children shows the same division into periods, only in a different order. The maximum period of growth in height corresponds to the minimum period of increase in bulk, and vice versâ. In September and October a child grows only a fifth of what it did in June and July. In other words, during a part of the year—autumn and beginning of winter—the child accumulates bulk, but the height is stationary. In the early summer the bulk remains nearly unchanged, but the vital force and the nourishment are expended to the benefit of height. While the body works for bulk there is rest for the growth, and when the period of growth comes, the working for bulk is suspended. The human body has, consequently, the same distinctly marked periods of development as plants.

A CHESS-CLOCK.

An ingenious clock has recently been patented by Messrs Frisch and Schierwater, 29 Church Street, Liverpool. It not only shows the ordinary time, but registers on separate dials—marked respectively ‘black’ and ‘white’—the period occupied by the players in a game of chess. It also indicates the number of moves in a game and whose turn it is to play. Another feature is the index upon the dial. This can be set for any time agreed upon—from one to fifteen minutes—during which a move must be made. The expiration of that time is shown by an indicator and by the ringing of a bell. By pressing a knob at the top of the clock, it is possible to temporarily check the progress of the mechanism. This would of course become necessary upon the players requiring a rest, or upon any other interruption taking place. The invention is, we believe, the first clock that has been constructed with a view to recording the movements in chess-playing. It may of course be utilised for other purposes. Being a travelling clock, it may be employed for indicating the times of different countries. The index and call-bell may be used, too, for public meetings, allowing so much time for each speaker; for a telephone Company, regulating an allowance of time; or for the testing of any machinery. The movement can be fitted to any existing clock. As a result of practical trial, the ‘Schierwater’s’ Patent Chess-Clock has been commended by many well-known chess-players.

NOVEL PHOTOGRAPHIC EXPERIMENTS.

The sinking of the caissons of the Forth Bridge has afforded opportunity for testing whether it was possible to obtain photographs below water in compressed air by the aid of electric light. To the novel conditions under which these attempts—the first, we believe, in this country—were made, their chief interest is due, rather than to any particular success hitherto achieved. We have recently described the method of founding by compressed air, and depicted the interior of a caisson, so that our readers are conversant with the surroundings under which the attempts were made.

A trial was made on shore by electric light at night to determine the length of exposure necessary for the plates; but subsequent experience proved the data thus obtained to be of little value in the air-chamber. Various trials were then made in the air-chamber with different classes of plates and gradually increasing lighting-power; eventually, five arc-lamps—each equivalent to twelve hundred candles—and plates of exceptional rapidity, were employed; and these, with an exposure of two minutes, gave the best results obtained.

The roof and sides of the air-chamber were whitewashed, to render them conspicuous and to diffuse the light. The formation of moisture on the lens threatened at first to give trouble; but after a little time the glass became warmed, and the difficulty ceased. The haze in the air-chamber, which any sudden expansion of the air—such as that due to its escape when the air-locks were opened—greatly intensified, proved a formidable obstacle, and must always render the highest results unattainable. The only course was to seize the most favourable moment when the haze was at its minimum. White objects and light clothing gave the best results; whilst the eyes of a group—presumably from their glistening properties—are remarkable for definition and sharpness.

So far as could be ascertained, no injury resulted to the dry plates either from air-pressure or moisture.

AN OLD ‘CHUBB.’

Last night I found an old forgotten key