on some ancient metallic Arms and Utensils. 427 
vations to suppose them to exist in the ancient metal instru- 
ments. It will be proper also to remark, that the only species 
of metals known till within the last two or three centuries, 
were gold, silver, quicksilver, iron, copper, lead, and tin. The 
oxides of several of the brittle metals were known indeed to 
the Hebrews, Greeks, and Romans, and perhaps to several 
barbarous nations of great antiquity ; but not one of them was 
used as an allay, except the oxide of zinc to compose artificial 
orichalcum. 
It appears that the metal of the spear-head contained silver; 
but although the presence of it was proved by a repeated de- 
cisive experiment, § 4. ( e ), the proportion of it was too small 
to alter sensibly the properties of the allay of copper with tin, 
and could not answer any useful purpose in such a compound. 
I therefore believe that the silver in this instance was not pur- 
posely added ; but was an accidental or natural ingredient of 
the copper, used for the making the metal of this spear-head. 
The Bishop of Llandaff made a few experiments on a celt, 
from which his lordship concludes that it seemed to contain 
zinc : for it emitted a blue flame, and a thick white smoke, on 
the first exposure of a piece to fire ; but no such appearances 
were seen on the second exposure of the same piece to fire. 
Every person will readily give credit for the observations being 
accurately made; nor would I even refuse to admit the con- 
clusion, that the celt examined by his lordship did contain zinc; 
but it is also just to observe, that a piece of copper, or of allay of 
copper, with tin, being exposed to fire in an open vessel, emits 
frequently a blue flame on a first, but not on a second exposure 
to fire soon after the first, § 4. (c) ; and if much air be admitted 
to the allay of copper with tin in fusion, a white smoke will also 
