148 Mr. Hatchett's Experiments on the various Alloys , 
impression produced, during friction, were uniformly the same 
in every direction. 
The first experiments were intended to ascertain the different 
wear of gold made standard by various metals ; and the pieces 
were rubbed against each other by means of the first-described 
apparatus, which I shall call No. 1. 
Some preparatory experiments were also made, to try the effects 
of this machine, as well as to determine, in some measure, the 
comparative wear of gold made standard by copper, of a mixture 
of gold and copper in equal proportions, and, lastly, of copper. 
Experiment 1. 
Twelve pieces of the standard gold were first examined, and 
were placed so that six were opposed to six. 
The brass frame, in which each upper piece was fixed, weighed 
1604 grains ; and it was found necessary to add to each a weight 
of lead, equal to 19825 grains; so that the pieces were rubbed 
against each other under the pressure of 19825+1604 = 21429 
grains = 3 lb. 8 oz. 12 dts. 21 grs.* 
The machine was then put in motion, until the index showed 
that 286690 revolutions had been performed ; and, as a double 
crank acted during each revolution, the pieces were rubbed 
against each other alternately, in opposite directions, 573380 
times, being twice the number of the revolutions. 
The twelve pieces of standard gold, being taken out, were 
weighed, and were found to have lost 8,60 grs. 
* This weight may appear to be very considerable ; but it was not employed until 
repeated trials had proved the extreme difficulty, and almost impossibility, of producing 
any perceptible effect within a moderate period of time; and, even with this weight, 
the experiments were found to be exceedingly tedious. The only evil which resulted 
from such a pressure was, that the comparative wear of the fine gold appeared much 
rpore considerable than would have been the case, if a small weight could have been 
employed ; some observations will therefore be found in the subsequent pages, which 
point out the necessity of making an allowance for this circumstance. 
