112 Mr. Hatchett's Experiments on the various Alloys , 
than that which ought to be produced, supposing this effect 
depended only upon the quantity of copper ; it may therefore 
be inferred, that the properties of a compound metal are peculiar 
to itself, and are in general different from the mean of the 
properties of the several metals employed to form the compound. 
The results stated in the foregoing Table, seem to indicate, 
that the assertions of many respectable authors, concerning the 
density of alloyed metals, should not be understood in an ab- 
solute or unqualified sense. 
Mr. Brisson, in his valuable work entitled Pesanteur sped - 
jique des Corps , has observed, that a mutual penetration takes 
place, when eleven parts of gold are alloyed with one of 
copper ; and, in consequence of this, that he found the specific 
gravity of gold alloyed with ~ of copper to be 17,486 ; al- 
though, if this mutual penetration of the two metals had not 
happened, the specific gravity ought to have been 17,153 ; but, 
in the course of the present experiments, the reverse of this has 
been observed ; for, instead of any mutual penetration of these 
metals, a very notable degree of expansion in the alloyed mass 
has been remarked. 
When 442 grains of gold, 23 car. sfe grs. fine, (the specific 
gravity of which was 19,172,) were alloyed with 38 grains of 
fine copper, of the specific gravity of 8,895, the mass was found 
to be of a specific gravity equal to 17,157 ; and, as the bulk of 
this alloyed mass amounted to 27,98, while the natural bulk 
of the two metals before combination amounted only to 27,32, 
there was consequently an expansion of the alloyed mass, equal 
to ,66. These calculations were made upon an intire ingot, 
weighing two ounces Troy, or 960 grains ; which mode appeared 
