160 Trans. Acad. Sei. 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 Ampere effect due 
to a special form of Rowland’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 
