164 ELECTRICAL PROPERTIES OF SILK. 
the operation just now mentioned, they had ac- 
quired the negative electricity, if they were placed, 
not upon the smooth body on which they had been 
rubbed, but on a rough conducting substance, they 
would, on their separation, show contrary electrici- 
ties, which would again disappear on their being join- 
ed together. If they had been made to repel each 
other, and were afterwards forced together, and 
placed on the rough surface above mentioned, they 
would in a few minutes be mutually attracted ; 
the lowermost being positively, and the uppermost 
negatively electrified. 
If the two white ribands received their friction 
upon the rough surface, they always acquired con- 
trary electricities. The upper one was negatively, 
and the lower one positively electrified, in what- 
ever manner they were taken off. The same change 
was instantaneously done by any pointed conductor. 
If two ribands, for instance, were made to repel, 
and the point of a needle drawn opposite to one of 
them along its whole length, they would imme- 
diately rush together. 
The same means which produced a change of 
electricity in a riband-already electrified, would 
communicate electricity to one which had not as yet 
received it, viz. laying the unelectrified riband up- 
on a rough surface, and putting the other upon it, 
or by holding it parallel to an electrified riband, 
and presenting a pointed conductor to it. He 
