208 A, M. Mayer—Researches in Electro-Magnetism. 
action of the outside of the helix the following experiments were 
made. Several wires 9 in. long and ;!; inch diam. were heated 
in a cupel furnace to bright redness and slowly cooled ; one end 
of each wire was then marked. wire was then taken and 
placed with its marked end 2°75 in. W. of the center of the 
compass-needle and the deflection produced was 8. 18’ E., show- 
ing that the marked end was a feeble S. pole. A current was 
now passed through the inner helix and the wire laid upon 
it so that its marked or 8. end was upon the S. pole of the helix, 
after remaining here for a few moments it was conveyed to the 
compass and placed, as before, with its marked end 2°75 in. W. 
of the center of the needle. The deflection was now 8. 28’ W., 
showing that the magnetism of the wire had been reversed and 
that a wire placed on the owtside of a helix has given to it a 
magnetism the reverse of that given when it is placed imside. 
Ex. 28. Twelve wires were now placed with their marked 
ends 3°25 in. W. of the needle, and the deflection being S. 8’ E. 
showed that their marked ends had aslight S. magnetism. They 
were now removed and placed with their marked ends on the N. 
pare of the helix at equal distances from each other around the 
elix, through which a current was passing; they were then re- 
moved from the helix before the current was broken and again 
laced in their former position 3-25 W. of the compass-needle. 
he deflection was now 8. 55’ E., showing that their marked 
ends were of south magnetism. They were again placed on the 
helix with their marked ends on its S. pole and removed, as be- 
fore; they now deflected the needle S. 20’ W., showing that their 
marked ends were now N., their magnetism having been reversed. 
Ex. 29. e inner helix alone was placed 1 foot W. of needle 
and the current passed so that its S. pole was opposed to the 
needle. Deflection S. 3° 80’ E. T. G. 20°. Reversed current. 
Deflection 8° 15’ W. By holding a bar of soft iron in the line 
of the dip and passing the wires over its end I succeeded in ren- 
dering them without action on the helix when put in the place 
of the helix in the above experiment. The twelve wires were 
then tied around the helix equidistant from each other and sepa- 
rated about ‘2 inch. The current was then passed so that the 8. 
ee of the helix was opposed to the needle. Deflection S. 2° 40’ 
.. Reversed the current. Deflection S. 2° 80’ W. We therefore 
have in the 1st experiment 50’ less and in the 2d 45’ less action 
on the needle when the wires are around the helix than when they 
are away. These results correspond to the above experiments 
on the tube, the helix giving the wire a polarity the reverse of 
its own. 
Beccaria, Coulomb and Faraday have, by their well known 
experiments, proved that frictional electricity when at rest only 
exists on or just within the outer surfaces of bodies, and Prof. 
