506 Mr. Babbage on electrical 
four, or five degrees ; so that the measure of the observed 
fact was from four to eight times the extent of the greatest 
possible error of observation, even admitting it to take place 
at both extremities. It is true, I did not always observe this 
retrograde motion ; but in twenty experiments the needle, 
screen and plate, not being always at the same relative dis- 
tances, I noticed it seventeen times. The next step seemed 
to be to find some mode of encreasing the unequal distribu- 
tion of electricity on the metallic plate, supposing that to be 
the cause of the phenomena. I therefore made a very small 
lamp, which being lighted, was placed on the stage L of the 
revolving apparatus, immediately under the copper. It was 
afterwards found convenient to make a small aperture in the 
lower millboard cylinder, just opposite the platform support- 
ing the lamp, for the purpose of lighting it when requisite : 
this opening was closed by a piece of mica, fastened on a card. 
Experiment 11. 
A small stick of sealing-wax being suspended from the 
silver wire above a leno muslin screen, the pewter plate 
was supported just above the lamp, and under the screen, 
the following observations were made : 
