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DISTURBANCES IMPRESSED UPON THE 

 EARTH'S MAGNETIC FIELD.* 



Francis E. Nipher. 



It is now thirteen years since the writer first made a 

 long series of experiments, in which an attempt was made 

 to reproduce, by means of explosions, the magnetic dis- 

 turbances due to solar outbursts. These results were 

 finally obtained at my summer home near Hessel, Mack- 

 inac County, Mich., during the summer of 1914. 



In these experiments, half a ton of rapid burning blast- 

 ing powder and 300 pounds of 40 per cent dynamite was 

 used. The expense involved was paid by the Carnegie 

 Institution of Washington. 



The magnetic needle and its enclosing case was fully 

 described in a former paper. 1 As in the work described 

 in the former paper, all possible precautions were taken 

 to make the case surrounding the needle air-tight. The 

 damping wire dipping into coal-oil in the bottom of the 

 glass bottle which formed the enclosing case, was only 

 1 cm. in length, in order to give to the needle more free- 

 dom of motion than it had in former work. The socket, 

 provided with leveling screws into which the bottle was 

 sealed, was securely clamped to the table. The top of the 

 tube of metal within which the suspension fiber was hung 

 from a torsion head, was braced by four bars of wood, 

 inclined at an angle of 45° with the vertical. Along these 

 bars were four heavy cords, attached to the torsion head, 

 passing down through the table. Upon these cords were 



* Presented by title to The Academy of Science of St. Louis, Decem- 

 ber 6, 1915. 



i Variations in the Earth's Magnetic Field. Trans. Acad, of Science 

 of St. Louis, XXII: 109-110. 1913. 



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