90 Mr. J* J. Waterston on some Electrical 



Appendage on B. D. Angle. 



o 



Tinfoil pointed and projecting \ inch from rim of B. D. 60 

 u „ 1 inch „ „ 15 



Sewing-needle, point projecting Jo inch. • ■ • • • • 70 

 „ „ | inch . . ... 42 

 „ head projecting j inch 70 



Silver-leaf, projecting ^ inch 44 



Silk thread highly dried in sand-bath, the end pro- "^ -. nn 

 jecting \ inch as a bush of extremely fine fibres J 



Without appendage 100 



Discharging effect of stroking. 



21. When the electroscope was charged to near its maximum, 

 a small disk of fine sealing-wax was placed upon the cap ; then 

 the elbow of a bent iron wire with a newly filed surface was 

 gently drawn along the top surface of disk, stroking it as it were. 

 This caused the leaves to descend to 50°, and on taking off the 

 disk from the cap the leaves rose again to their original angle, 

 and the disk was found electrified on the surface stroked. There 

 was no effect by merely touching the disk with the wire at many 

 points. 



Gold-leaf, silver-leaf, lead, brass, steel file, &c, employed in a 

 similar way, also reduce the angle to 50°, and not lower. 



The stroking of itself does not excite the wax surface when 

 the leaves are at zero. 



Note that all metals when rubbed on wax disk excite it posi- 

 tively, while silk and woollen excite it negatively. The charge given 

 to the electroscope may be positive in the above experiment, so 

 as to show that the effect is not due to excitement by rubbing. 



Discharging influence of flame and incandescent matter , and effect 



of screens. 



22. The insulated B. D. charged to a known degree (J charge 

 = 90°) was maintained in position 5 inches below a gas-flame, 

 the jet being horizontal, and the time measured by metronome. 

 When the flame was reduced to the very smallest possible blue 

 bead, the charge was reduced to = 40°. When the flame was the 

 largest possible (No. 2 burner), the reduction of charge was exactly 

 the same in the same time, viz. 90° x 4 to 40° x 1, or 1*2 toO'14 

 density of charge (fig. 10). 



23. A bead of gas-flame 2 inches above cap of charged 

 electroscope discharges it until the leaves close to about 1° ; cer- 

 tainly not entirely shut, because touching the plate with the point 

 of a penknife brings the leaves sensibly closer. 



At the distance of 4 inches the discharge proceeds so far as 



