specific Gravity , and comparative Wear of Gold. 1 23 
an hour, without being stirred or agitated ; it was then cast as 
before. 
The two extremities, being separated, afforded the following 
results. 
Spec, gravity. Quality by assay. 
1. Top - 17,203 - Better than standard, by 10 grains Troy. 
2. Bottom 17,38 7 - Better than standard, by 10 grains Troy, 
This last bar was, therefore, throughout of an equal quality; 
although it appeared that, by this second fusion, the whole mass 
was become finer, by two Troy grains, than it was in the former 
experiment; and the specific gravity of both ends was also be- 
come more considerable. 
In these two last experiments, the specific gravity of the bars 
was the greatest at the bottom ; and as by the assays it was 
proved, that each bar was of an uniform quality, it may be in- 
ferred, that when a bar of metal is cast in, or nearly in, a ver- 
tical position, a difference in the density of the mass takes place, 
independent of any change in the quality of the mixture, and 
that the greatest density prevails in the lower part of the column, 
or in that which suffers the greatest pressure from the superin- 
cumbent metal. It also follows, that this effect is subject to be 
modified by the quality and specific gravity of the metal, by the 
more or less vertical position of the mould, by the quantity of 
metal which is cast, and especially by the length of the bar, or 
height of the metallic column. 
There cannot be any doubt but that the same causes operated 
in those experiments which afforded results so precisely oppo- 
site to these last, in respect to the relative specific gravities of 
the extremities of the bars ; but then, the effect in question was 
much more than compensated by the unequal distribution of 
R 2 
