on some ancient metallic Arms and Utensils. 435 
which they were applied. This proportion being considered 
to be about one part of tin to nine parts of copper. 
Copper allayed with a larger proportion of tin than is ge- 
nerally contained in celt metal ; that is, with one-sixth or one- 
seventh of its weight of tin, is fitter for cutting instruments* 
and piercing, boring, and drilling tools than celt metal ; be- 
cause it is harder, takes a finer edge, and yet is sufficiently 
strong on most occasions ; nor do we possess at this day any 
metal, that I know, which is so fit for knives, swords, daggers, 
spears, drills, &c. as this allay, except iron and steel. 
The spear-head contains tin in the very proportion here 
mentioned ; and if the metals had been pure, it would not have 
been possible, perhaps, to have made this instrument of any 
other metals, which were so proper, and at so small an expence. 
The sauce-pan also was made of allay of copper by tin in 
the proportions last mentioned, § 7. p. 428 ; but as this instru- 
ment is sufficiently hard with less or without any tin, there 
seems to be no use from the addition of it. We may conjec- 
ture, indeed, that as the sauce-pan was made of cast metal, the 
tin was added for the purpose of rendering the copper more 
fusible, and thereby also for more easily casting forms of it. 
Perhaps also the tin was added to render the copper less readily 
oxidable, and for the colour of this composition. 
Copper united with the proportions of tin last mentioned 
is very sonorous ; but it is rendered much more so by still 
larger proportions of tin. I apprehend the sonorous property 
increases as the proportion of tin is increased, within certain 
limits ; provided the allay possess sufficient strength not to be 
fractured by the necessary impulse. But as the brittleness 
increases with the increased proportion of tin, I believe not 
