Page:Popular Science Monthly Volume 43.djvu/291

Rh in the movement of the transmitting and receiving instruments, a condition practically impossible of realization. Unlike these earlier devices, the system of Prof. Gray does not depend at all upon the timed movements of the instruments at each end of the line, but like the telephone the transmitter positively actuates the distant receiver. The fundamental principle of the apparatus is that first applied to this purpose by Mr. E. A. Cowper, of England, some fifteen years ago; but Prof. Gray has greatly simplified the construction and given a range and flexibility to the instruments which practically constitutes a new departure in this method of transmission. The principle involved is the familiar geometric one that any plain curve, no matter how intricate, may be decomposed into component parts along two lines at right angles to each other. If, then, a point be affixed at the junction of these lines, all that is necessary to reproduce its movements is to cause two other similar lines to reproduce the movements of the first two. A point at the junction of the second lines will then travel in exact conformity with the first point. This principle is made use of in the familiar draughtsman s instrument, the pantograph, used for producing enlarged or reduced copies of an original drawing. In Prof. Gray's apparatus the transmitting instrument consists of a box provided with a leaf or table, upon which the paper, which is fed from a roll mounted upon the instrument, rests. The pencil is placed at the junction of two silk threads at right angles to each other, the farther ends of which are wound upon drums in such a way that the motion of the pencil serves to rotate them backward and forward in exact accordance with the linear components of the curves described by it. These drums have each an arm which sweeps over a series of electrical contacts, thereby sending a succession of electrical impulses into its line wire proportional to its movement. A contact playing between stops serves to reverse the current with the reversal of the motion of the drums. The receiving instrument consists of a pen mounted at the junction of two light metal arms, the movements of which are controlled by the electrical impulses sent to line by the transmitting mechanism. This control is effected by means of a gear-wheel.—one for each metal arm—which is actuated by clutch-weights, which weights are in turn controlled by the current through the medium of an electro-magnet. The gear-wheels, therefore, move in one direction or the other in exact accordance with the currents sent over the line wires and give motion to the arms carrying the transcribing pen. The pen is of the ordinary form in such instruments, namely, a glass tube drawn out to a capillary bore near the point and supplied with a free-flowing ink.

Relations of Leaves and Boots.—As a result of investigations of the influence of manure on the development of roots, M. Dehérain has found that roots in unmanured ground have a larger growth than in manured, having to spread more in search of the scanty nutriment. It having been previously found that transpiration largely depends on the activity of the roots as well as on the evaporative surface, and is not, therefore, strictly proportional to leafy development, it follows that if a plant with small leafy growth evaporates relatively more water than one with more abundant foliage, it is probably due to large root-growth procuring more water. Volkens has observed that desert plants have extraordinarily long roots. M. Dehérain further points out that solar rays falling on a plant have the twofold work of assimilation and transpiration to perform, and that these are complementary. In strong, leafy plants, assimilation is vigorous, so that transpiration is limited; while in the leaves of an "anæmic" plant a large fraction of the solar energy is given to transpiration.

Folk Lore of the Kootenay Indians.—Among the Kootenay Indians of southeastern British Columbia there exist some strange ideas of mythology. Their folk lore is extremely picturesque, and bears strong resemblance to that of the earlier European and Asiatic races. The moon is regarded by them as a man, and the sun (natā-nik) as a woman. There was no sun in the beginning (according to the Kootenay-Indian mythology), but after the Indians had vainly endeavored to discover it, the coyote was successful in making it rise above the mountains. Another version makes the chickenhawk cause the sun to rise, and the coyote,