Scientific American Supplement, No. 344 (Aug 5, 1882), page 90 by Various
<< Return to Title Details & Download91
ction spark assumes when it is submitted to the action of a magnet in the direction of its axial line, or in that of its equatorial line, or perpendicular to these latter, or upon the magnetic poles themselves.
Experiments of a very definite kind have not yet been made as to the nature of the arc produced by induced currents developed in alternating current machines; but, from the experiments made with electric candles, we are forced to admit that the current reacts as if it were alternately reversed through the arc, since the carbons are used up to an equal degree; and, moreover, Mr. Pilleux's experiments show that effects analogous to those of induction coils are produced by the reaction of magnets upon the arc. There is, then, here a doubtful point that it would be interesting to clear up; and we believe that it is consequently proper to introduce in this place Mr. Pilleux's note:
"Having at my disposal," says he, "a powerful vertical voltaic arc of 12 centimeters in length, kept up by alternately reversed currents, and one of the most powerful permanent magnets that Mr. De Meritens employs for magneto-electric machines, I have been enabled to make the following experiments:
"1. When I caused one of the poles of my magnet to slowly approach the voltaic arc, I ascertained that, at a distance of 10 centimeters, the arc became flattened so as to assume the appearance of those gas jets called 'butterfly.' The plane of the 'butterfly' was parallel with the pole that I presented, or, in other words, with the section of the magnet. At the same time, the arc began to emit a strident noise, which became deafening when the pole of the magnet was brought to within a distance of about 2 millimeters. At this moment, the butterfly form produced by the arc was _greatly spread out, and reduced to the thickness of a sheet of paper_; and then it burst with violence, and projected to a distance a great number of particles of incandescent carbon.
"2. The magnet employed being a horseshoe one, when