specific Gravity, and comparative fVear of Gold. 171 
according to the result of this experiment, they had relatively 
sustained. 
The different pieces, after the experfment, had a curious 
appearance ; for, on the edges, which were become round and 
polished, a small regular raised bead or moulding was formed, 
which surrounded each face, like a frame; and both faces were 
become more or less concave. 
The original diameter of the pieces was also diminished, 
nearly according to their different degrees of ductility, and 
according to the loss which they had experienced in conse- 
quence of the operation. 
The measure of the diameters of the pieces, after the experi- 
ment, was, 
Gold 23 car. 3-I grs. eight-tenths of an inch and 
Gold alloyed withesilver, nine-tenths of an inch. 
The others varied little from nine-tenths and ~ ; which was 
less, by about ~ of an inch, than the original diameter of the 
pieces; and it was evident, that the pieces of fine gold and those 
consisting of gold alloyed with silver, being the most ductile of 
the whole series, had suffered the greatest loss, and also that 
they were those which became the most diminished in diameter. 
Upon the whole, therefore, considering the general result of 
this experiment, it appears to corroborate what has been asserted 
concerning the former experiments, viz. that soft or ductile gold 
suffers the greatest loss, when exposed to friction in contact with 
gold which is comparatively harder. The effects upon gold of 
23 car. 3^ grs. and upon gold alloyed with silver, fully prove 
this ; and, if a perceptible difference was not found between the 
others, in this experiment, it must be ascribed to the difference in 
ductility being too small to resist the general effect of the friction; 
Z 2 
