Page:Popular Science Monthly Volume 31.djvu/880

860 colors, and their capacity, on account of the large sections which they would afford, to furnish art-objects of unexampled qualities. Although it was thought that sections two or three feet in diameter might be produced, it has until very recently not been possible to get such sections polished. At last machinery was found competent to do the work; and Mr. Kunz was able to show some beautiful large specimens, which had been cut by a gang of seven saws and polished at Sioux Falls, Dakota, by water-power from the falls, on wheels fourteen feet in diameter. The objects exhibited included one column eleven and a quarter inches wide and twenty-one inches high, cut transversely across the tree so that the heart was visible on two sides of it, with the radiations in all directions; also five sections, measuring twenty-five, nineteen and a half, twenty-four, seventeen and a half, and thirteen inches in diameter, respectively, so highly polished that, when turned with the back to the light, they formed a perfect mirror. All of the specimens were brilliant in color.

Telephonic Communication between Ships.—Professor Lucien E. Blake described in the American Association a method which he had conceived in 1883 for making telephonic communication between ships at sea. A sound-producing apparatus was to be attached to each vessel, and to be worked under the surface of the water; and each vessel was also to have a sound-receiving apparatus, to take up the signals from other vessels. Signals, intelligible by means of a code, could be produced by this apparatus, which would be transmitted in all directions through the water with a velocity four or five times that in the air. For steamships the sound-producing apparatus was designed to be a steam fog-horn or whistle, specially constructed to sound under water, and to be heard at least six or eight miles off. With such whistles, a Morse alphabet, of long and short blasts and pauses, was to provide a means of extended communication, while a simple universal code would indicate a ship's course. Since ignorance of the very presence of a ship, rather than incorrect estimates of her course, has been the principal cause of ocean collisions, the simple hearing of the sound would prove a most excellent general safeguard. Bell-buoys were to have a second bell added under water, while lightships, lighthouses, and any headlands might also be provided with submerged bells, which could be rung from the shore when necessary. Sailing-craft would also have bells, which, if like ordinary locomotive-bells, could be heard at least two miles under water. By the method described, in October, 1885, signals were transmitted and received through one and a half mile in the Wabash River from a locomotive-bell, around three or four windings of the stream.

Teaching Physics in the Public Schools.—Professor W. A. Anthony, speaking in the American Association, Section of Physics, on the importance of teaching physical science in the public schools, said that proper scientific instruction in the primary schools would teach children to avoid the mistake of attempting the impossible. While grammar should be put off to the last, language should be taught by reading, not by rules; the geography, after teaching the form of the earth, should be used only as a book of reference; and the commercial departments of arithmetic should be relegated to the business-school; children in their earliest experiences have to do with heat, light, sound, movement, and magnetism. Physics should be taught by calling attention to familiar facts, and then explaining them.

Effect of Light on Bacteria and other Organisms.—Messrs. Downes and Blunt, in two papers read before the Royal Society in 1877 and 1878 on the effect of light on bacteria and other organisms, and on protoplasm, announced the conclusion that light is inimical to these organisms, and under favorable circumstances may wholly prevent their development. The effect was shown to be due to oxidation, which was stimulated by light, and ended in the extinction or in the great depression of the vitality of the organisms submitted to it. The authors furthermore declared that the maximum of the oxidizing effect was near the violet, or in the more refrangible rays, and was comparable with the chemical phenomena of