108 



SCIENCE 



[N. S. Vol. XLI. No. 1046 



marl loess of southwestern Indiana consists of 

 wind deposited true loess, stream laid valley 

 filling, and dune sand, and that the true loess 

 part of it together with the " common loess " 

 corresponds to the well-known loess of other 

 parts of the Mississippi basin. 



Eugene Wesley Shaw 



SOCIETIES AND ACADEMIES 



ST. LOUIS ACADEMY OF SCIENCES 



At a meeting of the Academy of Sciences of St. 

 Louis, held October 19, Professor Nipher gave an 

 account of his work during the summer of 1914, at 

 his summer place in Hessel, Mich., on "Magnetic 

 Disturbances in the Earth's Field due to Dyna- 

 mite Explosions, Burning Black Powder and the 

 Fog-horn of a Steamer. ' ' 



The magnetic needle was mounted on a frame of 

 timber, the vertical posts of which were set two 

 feet into the ground. The frame and the boxes 

 containing the control magnets were loaded with 

 half a ton of rocks. The boxes containing the con- 

 trol magnets were also clamped to the frame with 

 large wooden clamps. The base of the air-tight 

 vessel containing the magnetic needle was also 

 clamped to the frame. The torsion head was 

 braced by means of wooden bars. Four cords at 

 right angles to each other were attached to the 

 torsion head. They passed outward and down- 

 ward through holes in the table, and upon them 

 were hung two bars of wood at right angles to 

 each other. These bars were also loaded with rock. 

 The apparatus was protected from heat effects by 

 a series of blankets within the tent, having air- 

 spaces between. 



No difficulty was found in producing marked 

 local disturbances in the earth's field by means of 

 dynamite suspended in air to the east and to the 

 north of the tent. The needle being at right 

 angles to the magnetic meridian, this disturbance 

 indicated a variation in the horizontal intensity. 



The amount of dynamite exploded varied from 

 half a stick six or eight feet from the tent, to 

 thirty sticks distant 275 feet. In the larger ex- 

 plosions, the sticks were placed end to end on bars 

 of wood having a cross section 1X14 inch. Each 

 stick of dynamite was securely held in place upon 

 the bar by means of a winding of heavy cord. The 

 ends of the bar suffered no appreciable injury. 

 Those parts in contact with the dynamite vanished 

 in. dust so fine that it was difficult to find any trace 

 of it. The changes in the position of the needle in 



explosions of this character amounted to ten or 

 fifteen minutes of arc. 



Much more marked effects were produced by 

 distributing half a stick of dynamite into a col- 

 umn about 15 feet in length.' It was packed closely 

 into the angle of a little trough of wood, which 

 rested upon a heavy beam of wood. The trough 

 was held in position by means of masses of rock 

 hung on cords. The column of dynamite was in 

 line with the needle and either above or below the 

 level of the needle. In this way deflections of 

 about one degree of are were produced. The di- 

 rection of deflection was reversed by reversing the 

 direction in which the explosion traversed the col- 

 umn. The end of the column nearest the needle 

 was distant from it about ten feet. 



This seems to indicate that a magnetic field is 

 created around this exploding column, like that 

 which exists around a wire conductor carrying a 

 current of electricity. In most of the experiments 

 of this character only a small part of the column 

 exploded. It is believed that the conditions which 

 will cause an explosion of the entire column with 

 equal violence throughout have been finally at- 

 tained, and this work will be continued. 



The black powder was spread over a platform hav- 

 ing an area of 25 square feet, placed a few feet from 

 the west side of the tent. The amount of powder 

 spread over the platform was from 25 to 50 pounds. 

 The flame shot upward to a height of 15 to 30 feet. 

 The lines of the earth's field were defiected around 

 the region filled by this flame. The intensity of 

 field within the tent was momentarily increased. 

 The deflection of the needle amounted to from 25 

 to 50 minutes of arc. 



At the request of Professor Nipher, the captains 

 of the steamers of the Arnold Transit Co. were in- 

 structed by the president, Mr. Geo. T. Arnold, to 

 blow a loud and prolonged blast on their fog-horns 

 when at the nearest point to the observing station. 

 This distance was about half a mile. Appreciable 

 effects were thus produced when the air was quiet, 

 the sky was clear and the intensity of the field 

 had reached a high value. The result in every 

 case was to decrease the intensity of the earth's 

 field. 



In two cases the blast from the 5 o'clock boat 

 was at once followed by a premature appearance 

 of the sunset disturbance. Ehythmical vibrations 

 over from 10 to 20 degrees of arc at once fol- 

 lowed, and continued for four or five minutes. 

 This result needs further examination under more 



favorable conditions. „ „ 



C. H. Darforth, 



Secording Secretary 



