1 ^6 Mr. Hatchett’s Experiments on the various Alloys , 
This contrivance, therefore, effectually prevented the pieces 
from moving upon each other always in the same line; and it 
seems also to have much diminished the disposition which they 
had to wear in gullies, but not intirely ; for, from the following 
experiments it appears, that still some few particles would be- 
come occasionally collected, and then acted as a grinding 
powder, which accelerated the wear of the pieces. This was 
observed particularly to happen to the pieces of gold alloyed 
with an equal proportion of copper, and to the pieces of copper, 
which were also more frequently worn in furrows or gullies, 
than the other pieces of more ductile metal. 
The motion of the pieces of coin upon each other, is greater 
than it would have been if only one frame had been made to 
move, nearly in the proportion of 3 to 2 ; so that the whole 
motion of the pieces, in each semi-revolution of the axes EE or 
ee , is about -f of an inch, and therefore it is about three inches 
in each revolution of the windlass. 
The instrument employed in the second series of experi- 
ments, is so simple as not to require any drawing. It consisted 
only of a cubical box of oak, which measured 8 inches each way, 
within side. This box was moved by the axis EE of the former 
instrument, which was passed through the middle of two op- 
posite sides, and was fixed in that position. 
Fig. 4, represents a plan of the instrument used in the third 
series of experiments, aaa is a horizontal table, turning upon 
a vertical axis ; and BBB666 is a fixed frame surrounding it. 
The pieces of coin are fastened to this fixed frame, by the 
same connecting pieces which were formerly employed, and are 
pressed down also by similar weights. The diameter of that 
part of the wheel against which the centres of the pieces of coin 
