on some ancient metallic Arms and Utensils. 437 
more brittle, for the purpose of writing upon it, or marking it 
with lines and figures, as on mathematical instruments : but 
the allay with zinc is now preferred for these purposes, as I 
suppose on account of its being less hard than allays with tin, 
and yet sufficiently brittle ; on account also of its golden co- 
lour ; and also on account of its being still more difficultly 
oxidable by air and water. 
The scabbard metal contained a rather larger proportion of 
tin than the celts, No. 1. and No. 2. ; namely, being one-tenth 
of its w'eight, § 7. p. 429. Copper allayed by zinc would have 
been sufficiently hard and strong, and on other accounts pre- 
ferable to the allay of copper with tin. This is, however, one 
proof of the extensive use of this last composition among the 
ancients. 
The art of allaying copper with an earth-like substance ; 
which, within a little more than these fifty years only, we have 
learned was an ore of a metal, namely, zinc ; w ; as known per- 
haps in the time of Aristotle, and certainly of Pliny ; for the 
latter informs us, that this composition resembles orichalcum ; 
and after his lime it was called orichalcum. Thus the native and 
factitious orichalcum were confounded. The ancients do not 
appear to have used the allay of copper by zinc, except for 
mere ornaments, to resemble gold. It is much more exten- 
sively employed by the moderns, and the allay of copper with 
tin is less extensively used : 1st, because the former is cheaper 
than the allay of copper with tin ; 2dly, because it is now ge- 
nerally understood that it preserves its colour longer ; 3dly, 
because it is easier to work it into various forms, and especially 
for philosophical instruments ; few of which were probably 
made by the ancients. 
