specific Gravity , and comparative Wear of Gold. 181 
To judge from the unstamped pieces, it should seem as if a 
variation in the quality of the gold tended rather to diminish 
the wear ; but, from the effects of the stamped pieces, which 
are more to be regarded, it seems otherwise. Upon the whole, 
however, it does not appear to be a matter of much consequence, 
that the coin should consist intirely of gold of exactly the same 
quality. 
In the following experiment, filings of iron were employed, 
and were fixed upon the horizontal table by a solution of isin- 
glass. The leaden weights, and the general arrangement, re- 
mained as before. 
Experiment iv. 
Table XIII. 
Number of revolutions, 404. 
Quality. 
Weight be- 
fore friction. 
Weight after 
friction. 
Loss. 
Gold 23 car. 3-f grs. unstamped 
Grains. 
276,40 
' Grains. 
251,40 
Grains. 
25 
Gold 23 car. 3-^ grs. stamped 
278,30 
251,10 
27,20 
Gold made standard by silver, 
unstamped 
264,90 
244,90 
20 
Gold made standard by silver, 
stamped 
265,70 
23940 
26,30 
Gold made standard by silver 
and copper, unstamped - 
281,30 
258,50 
22,80 
Gold made standard by silver 
and copper, stamped 
278,80 
252,70 
26,10 
Gold made standard by fine 
copper, unstamped 
26l,20 
240,90 
20,30 
Gold made standard by fine 
copper, stamped 
239,20 
212,30 
26,90 
