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THE POPULAR SCIENCE MONTHLY. 



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 ma- 

 chinery 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 diame- 

 ter. The objects exhibited included one 

 column eleven and a quarter inches wide 

 and twenty-one inches high, cut transverse- 

 ly across the tree so that the heart was 

 visible on two sides of it, with the radia- 

 tions 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 18S3 for making tele- 

 phonic communication between ships at sea. 

 A sound-producing apparatus was to be at- 

 tached 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 blast3 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 pres- 

 ence of a ship, rather than incorrect esti- 

 mates of her course, has been the principal 

 cause of ocean collisions, the simple hear- 



ing of the sound would prove a most excel- 

 lent 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 locomo- 

 tive-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 

 stream. 



three or four windings of the 



Teaching Physics in the Public Schools. 



Professor W. A. Anthony, speaking in 

 the American Association, Section of Phys- 

 ics, 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 rele- 

 gated to the business-school ; children in 

 their earliest experiences have to do with 

 heat, light, sound, movement, and magnet- 

 ism. Physics should be taught by calling 

 attention to familiar facts, and then ex- 

 plaining 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 pro- 

 toplasm, 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 com- 

 parable with the chemical phenomena of 



