5 14 
Mr. Babbage on electrical 
of the plate, the torsion, which was previously supposed 
favourable for the reversed motion of the needle, would now 
act against it ; I therefore made the following experiment. 
Experiment 15. 
The motion of the copper plate was reversed, and reading 
in the new direction, the following were the mean positions 
of the wax needle. 
15.6 
16.0 
The lamp lighted. 
15.0 
Observation lost. 
2.0 
1.1 
31-5 
37.2 
38.3 
455 
30-3 
The greatest regression of the mean point of the needle 
was nearly 14 0 ; so that if torsion had any influence on the 
former experiments, it was unfavourable to the production of 
the retrograde motion. 
Experiment 1 6 . 
A screen of sheet zinc, about inch thick, was placed 
under a needle of sealing-wax, at about inch below it. 
The lamp was placed on the platform below, having its wick 
at the distance of about an inch from the zinc. The follow- 
ing observations were made. 
