522 Mr. Babbage on electrical 
which no heat was employed, and many of the subsequent 
ones in which no wire was used, effectually refute this 
supposition. 
7th. The electricity of the bridge might be supposed to 
produce some of the motions. 
It was more necessary to get rid of the action of this 
cause than of any of the others, because electricity, modified 
indeed by the circumstances under which it was placed, did, 
in my opinion, produce the whole of these curious pheno- 
mena. The action of the glass or wooden support was 
apparent, and is noticed in the remarks on the 19th Experi- 
ment ; but as it was not employed in any of those experi- 
ments in which the balance of torsion was used, and as it 
was dismissed from several of the latter ones in which re- 
versed motions of the needle appeared, they cannot be attri- 
buted to this cause. 
8th. The bending of the wax needle. 
The application of heat after some time altered the form 
of the wax needle ; it sometimes became so soft as to bend 
by its own weight down to the graduated circle. This 
change, however, only took place at the latter part of the 
experiment in which it occurred, and the phenomena re- 
corded usually appeared at a much earlier period, when if it 
had commenced the change was quite imperceptible. In 
those experiments in which heat was not employed this cause 
was absent ; and in many of those in which it was applied, a 
needle of card, or of thin brass covered with sealing-wax, or 
a mixture of resin and shell lac, was used, in which no bend- 
ing took place. 
Having shown that none of the causes to which I have 
