VOL. LXXXVI.] PHILOSOPHICAL TRANSACTIONS. 51 



of copper. — 3. The celt, N° 3, a little more than 12 per cent, of tin; that is, 

 about 1 part of tin, and 74- parts of copper. — 4. The lituus, nearly the same pro- 

 portions of tin and copper as the celt, N° 3. — 5. The scabbard, a little more 

 than 10 per cent, of tin ; that is, about 1 of tin and Q parts of copper. — 6. The 

 celt, N° 1, a little more of tin than Q per cent. ; that is, about 1 of tin and 10 

 parts of copper. — 7- The celt, N°2, the same proportions of tin and copper, as 

 in the celt, N° 1. 



6. The last 2 conclusions are confirmed by the exact correspondence between 

 the ancient metals and the allays of copper by tin, in external and obvious proper- 

 ties, § 2 and § 6 ; in specific gravities, § 3 ; and in chemical properties, § 5 and 

 ^ 6. Allays of 5 to 18 parts of copper with 1 part of tin can generally be distin- 

 guished from such allays with the addition of a very small proportion of the other 

 metals ; by the colour of their polish, the colour and texture of their grain, their 

 strength, their hardness, their malleability, and specific gravities ; without the aid 

 of chemical analysis. It is worthy of remark, that these allays of copper with tin 

 are evidently different, in their colour and grain, from such allays with the addition 

 of even V-o tn of their weight of zinc, exper. 13th ; and also from copper allayed by 

 ■^Vth of its weight of zinc, exper. 14th. 



The similarity of the properties of the ancient metals, and of the allays of 6 to 

 1 2 parts of copper with 1 of tin, is very evident. But with smaller proportions of 

 tin we find the allays are softer, and the grain of their fractures more open than 

 the ancient metals, experiment 1 — 4. ; and with larger proportions of tin we 

 find the allays harder, more brittle, paler, and closer in texture than the an- 

 cient metals, experiments — 11. It is right, however to remark, that the pro- 

 perty of hardness of the allays of copper by tin is, caet. pan as the proportion of 

 tin, or nearly so; which is not the case with some of the ancient metals; for the 

 spear-head and sauce -pan contain rather more tin than an equal quantity of the li- 

 tuus, § 5, (c), which is much harder than they, § 2. (c) ; and the spear-head and 

 sauce-pan are nearly as soft as the celts, N° 1 and N° 2, § 2, (c), which contain 

 the smallest proportion of tin of any of the old metals, § 5, (c). 



The grain also of the fractures of the spear-head and sauce-pan, before melting, 

 is much coarser, or open, than those of the other ancient metals which contain a 

 smaller proportion of tin, § 2, (b) : but it appears from the synthetic experiments 

 that the grain becomes finer as the proportion of tin is increased, § 6, exper. 1 — 

 12. To account for these inconsistencies I must remark, that a minute quantity 

 of extraneous unmetallic matter may be contained in metals ; so minute indeed as 

 to elude the most rigorous analysis, or at least not to be discoverable by the ordi- 

 nary modes of examination ; and which also may not render the metal at all unfit 

 for most of the uses to which it is applied. For instance, good malleable iron 

 may contain carbon, and even phosphate of iron or siderite ; and metals in general 

 may contain a very small proportion of oxygen, and yet be as useful as the purest 

 metals. The best English copper is accounted less tough and ductile than Swedish 

 copper. The purest English tin crackles when it is bent or chewed, but pure 



h 2 



