160 ELECTRICAL PROPERTIES OF SILK. 
lized stones, all resinous compounds, and all dry 
substances, such as silk, hair, wool, paper, &c. 
Silk was first discovered to be an electric by Mr 
Gray, in the manner we have already related ; but 
as it was by no means remarkable for emitting 
sparks, which most commonly engages the atten- 
tion, its electric virtues were almost entirely over- 
looked till the year 1759. At that time Mr 
Symmer presented to the Royal Society some pa- 
pers, containing a number of very curious experi- 
ments made with silk stockings, in substance as 
followse— 
He had been accustomed to wear two pairs of 
silk stockings, a black and a white. When these 
were put off both together, no signs of electricity 
appeared; but on pulling off the black ones from 
the white, he heard a snapping or crackling noise, 
and in the dark perceived sparks of fire between 
them. To produce this and the following appear- 
ances in great perfection, it was only necessary to 
draw his hand several times backward and forward 
over his leg with his stockings upon it. 
When the stockings were separated, and held at 
a distance from each other, both of them appeared 
to be highly excited ; the white stocking positively, 
and the black negatively. While they were kept 
at a distance from each other, both of them appeared 
inflated, to such a degree, that they exhibited the 
entire shape of the leg. When two black or two 
