is8 Mr. Hatchett’s Experiments on the various Alloys, 
as this was not the case, I am induced to be of opinion, that 
the specific gravity was again increased, by the subsequent 
stamping of the annealed pieces. 
In addition, therefore, to those causes of variation in specific 
gravity which are the immediate consequences of hydrostatical 
operations, such as, the different height of the column of water, 
and the changes of temperature to which it is exposed during 
the experiments, the following, as far as they concern metallic 
substances, may be enumerated. 
1. Imperfections in the interior of the mass, which are pro- 
duced during the processes of melting and casting. 
2. The difference of density in parts of the same mass, re- 
sulting from the quality and quantity of the metal, from the 
nature of the mould, from the more or less vertical position of 
it, and from the height of the column or bar of metal which is 
cast. 
g. The unequal distribution of the metal, or metals, employed 
as an alloy, throughout the mass intended to be alloyed. 
4. The peculiar effects which certain metals produce, when 
used singly or conjointly as alloys, and which are very different 
from the results of calculation.* 
5. Heat, whether produced by friction or excited in any other 
manner. 
* There can be no doubt but that the effects of compound alloys are, in general, 
very different from those of each metal separately considered ; and that such metallic 
combinations or compound alloys, like neutral salts, and many other compounds, 
have peculiar properties, which act variously upon the metals to which these com- 
pound alloys are added. A great number of accurate experiments are, however, 
requisite to elucidate a question so intricate. 
It may here be also observed, that the peculiar properties of compound alloys, prove 
£hem to be real chemical combinations. 
