43 ° , 
Dr. Pearson's Observations 
than the ancient metals, Exper. 1 — 4. ; and with larger pro- 
portions of tin we find the allays harder, more brittle, paler, 
and closer in texture than the ancient metals, Exper. 8. — 11. 
It is right, however, to remark, that the property of hard- 
ness of the allays of copper by tin is, ccet.par. 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 ra- 
ther more tin than an equal quantity of the lituus, § 5. (c), 
which is much harder than them, § 2. ( c ); and the spear-head 
and sauce-pan are nearly as soft as the celts, No. 1 and No. 
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 ), p. 404, 1. 21 : but it appears from the synthetic experi- 
ments that the grain becomes finer as the proportion of tin is 
increased, §6. Exper. 1. — 12. To account for these in- 
consistencies I must remark, that a minute quantity of extra- 
neous 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 ordinary 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 oxy- 
gen, 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 Malacca tin has not this property. These 
