Mr. Babbage on electrical 
5 04 
some neighbouring body, are removed with the same velo- 
city, The analogy of a fluid similarly circumstanced, would 
lead us to infer, that when the deviations above the level are 
minute, the return to it will be more slow. 
Of Screens. 
Although the preceding experiments, when repeated under 
various circumstances, had convinced me that the rotations 
which had been observed were not attributable to currents 
of air set in motion by the apparatus employed, I was de- 
sirous of examining what effect would result from the inter- 
position of a screen. I therefore suspended the needles I 
employed by a silver wire, T ~ inch in diameter, and about two 
feet in length, which was contained in a glass tube, supported 
over the middle of the apparatus represented in fig. 1. This 
tube and wire passed through a circular hole in the centre of 
the glass plate R. The bridge b 6, was removed, and a 
screen of fine muslin was stretched across the bottom 
of the lower cylinder O, by means of the external one c c . 
This screen and the needles were occasionally changed. 
Experiment g. 
A brass needle, having a very fine thread of spun glass 
cemented to one end by a little wax, was suspended by the 
silver, about ~ inch above a screen of coarse gauze (not silk). 
A pewter disc, of 4 inches in diameter, was placed on the 
revolving stand, T \ inch below the gauze screen. Neither 
the needle nor the disc were electrified ; and they were 
completely protected from any currents of air moving about 
in the room in which these experiments were made. 
