92 A, M. Mayer—KEffects of Magnetization 
if the quantity of this elongation was in any way due to the 
suddenness of the magnetizing action, and whether the elonga- 
tion produced by a certain current which is gradually brought 
sa 
strength. This problem was also connected with a proposed 
simple and accurate means of measuring the changes in dimen- 
sions of bodies subjected to magnetization, and I have therefore 
examined it with*care in the following manner. I cut the 
thick copper wire leading from the battery to the helix and 
firmly attached one of its loose ends to a support. Between 
this copper wire and the opposite wall I stretched a fine wire of 
german-silver. The other loose end of the battery wire was 
bent into a sharp angle and the vertex of this angle was 
well amalgamated. Now by sliding this bent copper wire along 
the fine wire of german-silver toward the other copper wire, I 
could gradually diminish the resistance,.and on touching the 
other end of the thick battery wire, this interposed resistance 
vanished and the current gained its maximum strength. On 
slowly retracing our steps the resistance was gradually increased, 
until the whole length of the fine wire was interposed, and then 
the resistance was at its maximum and the strength of the cur- 
rent was at its minimum. But if we brought the two amalga- 
mated ends of the copper wire in contact, either with or without 
the intervention of a mercury cup, we at once could suddenly 
send the current with its maximum intensity through the helix. 
Mean results of 1st series of experiments. Resistance of fine wire 
= 6 ohm. One cell in circuit. 
On gradually diminishing the resistance. 
Fraction of length of fine interposed wire. 
' t 25-28. pa ee. 
Scale-readings went from 54°8 to 54°85 54°9 55 55:2 55°6 56°1 
On gradually increasing the resistance. 
Scale-readings went from 55°5 to 54°8 55°6 55:8 55°9 55°95 56'l 
Tangent galvanometer, 7 oa a 
Mean results of 2d series of experiments. Resistance of fine wire 
="9 ohm. One cell in circuit. 
On gradually diminishing the resistance. 
Scale-readings, 54°8 54:8 54°85 55 55:4 5671 
On gradually increasing the resistance. 
Scale-readings went from 55°25 to 54°8 55:4 55°65 55°8 55°9 56°1 
Tangent galvanometer, ge ‘ 293° 
