A. M. Mayer—Researches in Electro-Magnetism. 107 
ise and sats Hain ser core gis sak this difference amounting 
The former experiments show that the tube can give a reversed 
magnetism to an enclosed core, and we will now see that a 
helix can effect a reverse magnetism on a surrounding tube. 
The first Expts. were made with opposing naa one hirit 
helix E with the 400 wire core, the other a tube of soft iron 9 
in. long, 1°3 in. external diam. and ‘12 thick, eter “whieh was 
wrapped a helix of one layer Py 148 turns of ;'; inch wire, and 
in its interior fitted a helix also of one layer ‘148 turns of the 
same wire wrapped upon a cylinder of a This last I will 
call the inner helix, the other the outer he 
Ke The inner helix was placed in the cireuit (near the 
battery, far removed from the compass) and the compass was so 
placed that its needle stood at 0° when circuit was open or closed. 
e inner helix was now placed inside the tube and the current 
passed through helix E and the outside ag and also through 
the inside helix in a direction the same as the current in the 
outer helix ; and the needle was Oak! The current was now 
reversed in the inner helix and needle again noted; but as the 
opposing helices were 8 ft. apart, and the current not strong, no 
effect (after allowance made for direct action of inner helix on 
needle) Me obtained from the action of the inner current. 
Ex. 26. I then devised the following experiment. 
posing helix EK with 400 wire-core was removed and the compass- 
needle brought to 0° by the action of the earth’s magnetism 
The iron tube was then placed 1 foot W. of center of needle with 
its S. pole toward the compass. The deflection alo by its 
magnetism was S. 4° 40’ HK. Theinner helix w 
in the position W. a the compass previously picket a by th the 
tube and the current passed so that its S. pole was op to 
the needle; the deflection was S. 3° 13’ E. I now placed the 
helix in the oe and both 1 ft. W. of needle and passed current 
so that S. end of pete was in S. end of tubes. "he deflection 
produced was 8. 4° 50’ E. 
rom above it ‘a seen that when tube and inner helix act 
together on the needle the deflection is only 10’ greater than 
when the tube acts alone, although the helix acting alone causes 
a defisetion of 3° 13’. The neutralization of such a quantity of 
magnetism can only be ian for by the fact that the great- 
er part of the magnetism of the tube was reversed by the action 
of the heliacal current on the inner surface of the tube. 
Ex. 27. To obtain directly a reversed magnetism by the 
