434 
Dr. Pearson's Observations 
of these two metals are used at different manufactories ; but I 
believe that this gun metal seldom contains less than one part 
of tin to twelve of copper, nor more than one part of tin to 
nine of copper. Here as much strength, as is consistent with 
the preservation of the figure of the instrument during its use, 
is required : and if more tin were added, the gun would be 
liable to be fractured by the explosion ; and if less were added, 
it would be liable to be bent. 
Copper allayed with a somewhat larger proportion of tin 
than in gun metal in general, affords a metal sufficiently hard 
and strong for chopping tools, for many useful purposes. Of such 
proportions, namely, about eight or nine parts of copper and one 
part of tin, there is very little doubt all the ancient nations, who 
were acquainted with the allays of copper by tin, generally made 
their axes, hatchets, spades, chizzels, anvils, hammers, &c. 
These metals, united in these proportions, would, I believe, af- 
ford the best substitute known at this day for the instruments 
just mentioned, now commonly made of steel or iron. Ac- 
cordingly, before the art of manufacturing malleable iron from 
cast iron was known at all, or at least practised extensively, that 
is, till within these last four or five hundred years, the allays of 
copper by tin must have been very generally employed. The 
celts may be considered as specimens of the kind of metal tools 
in general use before the art of manufacturing iron in the man- 
ner just mentioned was discovered : for, as hath been remarked 
in a former part of this paper, the celts seem to have been ge- 
nerally neither more nor less than metal heads of hatchets, and 
axes, or other chopping tools. And it is no small confirma- 
tion of this opinion, that by analysis and synthesis we have 
found those metals to contain, in perhaps most instances, the 
proportion of tin which renders them most fit for the uses to 
