50 PHILOSOPHICAL TRANSACTIONS. [ANNO 17Q6. 



ceding experiments and observations to suppose them to exist in the ancient metal 

 instruments. It will be proper also to remark, that the only species of metals 

 known till within the last 2 or 3 centuries, were gold, silver, quicksilver, iron, cop- 

 per, lead, and tin. The oxydes 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 oxyde of zinc 

 to compose artificial orichalcum. 



It appears that the metal of the spear-head contained silver ; but though the pre- 

 sence of it was proved by a repeated decisive 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 purposely added ; but was an accidental or 

 natural ingredient of the copper, used for 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 2d 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 conclusion, 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 2d 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 sometimes be seen ; 

 as was observed in the preceding experiment, § 4, (e). 



I suspect that the blue flame from copper when first ignited, and which ceases 

 on fusion, is produced by the inflammation of a little of the copper already com- 

 bined with oxygen ; for some oxydes of copper are so combustible, that if a small 

 part of a given mass of them be ignited, the ignition will spread rapidly throughout 

 the whole mass. Most probably celts were originally chopping tools, as we have 

 shown in a former part of this paper, and therefore the addition of zinc to the allay 

 of copper with tin would answer no useful purpose. 



5. The 5th conclusion relates to the proportion of the copper and the tin to each 

 other, in the ancient metals. I endeavoured to estimate the proportion of tin, by 

 comparing the quantities of oxyde of tin obtained from the ancient metals, with 

 the quantities of oxyde of tin obtained by the same means from allays of copper 

 with known proportions of tin. It appears from the analysis of the allays of cop- 

 per by tin, that the oxyde of tin afforded by the nitric acid solution is in the propor- 

 tion of about 150 parts from every 100 parts of the metal tin, § 6, ex per. 1st — 

 9th. According to this datum the proportion of tin in the old metals is in the 

 following proportions, or nearly so. 1. The sauce-pan contains of tin a little more 

 than 14 per cent. ; that is about 1 part of tin and 6 of copper, — 2. The spear- 

 head contains 14 per cent of tin ; that is, somewhat less than 1 part of tin and 6* 



