160 Trans. Acad. Sci. of St. Louis. 



These results have been repeated in the laboratory at 

 St. Louis during the spring of 1915. Deflecting magnets 

 which were balanced against each other on a needle 

 which was rendered sensitive by compensating magnets 

 were used, as in former experiments. One of the deflect- 

 ing magnets was much feebler than the other, so that 

 it was nearer to the needle than the other. The air around 

 the smaller magnet was electrified. A musical note from 

 an organ pipe produced effects which were superposed 

 upon other disturbances of similar magnitude. The ef- 

 fect of the musical note was appreciable, although at 

 times the other disturbances interfered with the result. 

 The blast of air from a compression tank, by means of 

 which the organ pipe was operated, produced more 

 marked results. The blast of air from a rubber tube was 

 directed through the space between the smaller deflecting 

 magnet and the metal shield around the needle. 



During the summer of 1914 an attempt was made to 

 examine the magnetic field around a column of exploding 

 dynamite. The effect sought was an Amp^e effect due 

 to a special form of Eowland's convection current. A 

 half stick of dynamite was crumbled into fine powder, 

 and packed into the angle of a wooden trough made from 

 bars of wood. The explosive cap was placed at the end of 

 the column. The trough was placed in the position shown 

 in Plate XXXVII, Fig. 2. It was in line with the needle 

 and eight inches above the level of the needle. The inner 

 end of the trough was about ten inches from the tent and 

 about 7 feet from the needle. Great difficulty was found 

 in making the entire column explode. In two cases a 

 complete explosion of the column, having a length of 15 

 ft. occurred. In these cases the wood of which the trough 

 was made was of very inferior quality and the entire 

 trough was shattered into small splinters which were 

 scattered over a distance of 30 ft. In these two cases 

 the cap was placed at opposite ends of the column. The 

 needle was deflected in opposite directions in the two 

 cases. The deflection was such as would be caused by 



