162 Mr. Hatchett’s Experiments on the various Alloys, 
From this comparative Table it appears, that although the 
experiments were made with correct instruments, and with every 
possible precaution, yet perfect accuracy could not be attained, 
nor indeed expected ; for, various minute and unavoidable cir- 
cumstances contributed to produce very sensible effects ; even 
a few particles, collected and retained between the pieces during 
the operation, frequently prevented the loss by friction from 
being correctly ascertained. Another cause of irregularity in 
the comparative wear of the pieces, arose from a small degree 
of unevenness in the level of many of the unstamped faces, 
which, although scarcely perceptible to the eye, became suf- 
ficiently apparent when friction commenced, and pointed out 
the necessity of relying only upon general results. It would 
not, therefore, be right to lay too great a stress upon very 
small and only occasional deviations in the results ; and con- 
sequently the small difference of a few fractional parts do not 
merit attention ; for the same reason, it would not be proper 
to form an opinion upon certain results, which, without any 
very apparent cause, seem to be in opposition to each other. 
The most candid and certain mode to be adopted, under these 
impediments, appears therefore to be, that of taking into con- 
sideration only such effects as were general, under every change 
of circumstance, and which were invariably more or less the 
same, however the mode of operation might be diversified. 
Upon this basis it may be concluded, that the preceding expe- 
riments prove, 
ist. That fine gold, or of 23 car. 3^ grs. when exposed to 
friction against gold of an equal quality, under the pressure of 
a considerable weight, suffers a very notable loss ; and, although 
various circumstances seemed to indicate that but little effect, in 
