Tin. 
369 
when cold it is divided horizontally into three layers; that 
the uppermost being very soft pure tin, is afterwards 
mixed with copper, in the proportion of 3 pounds of cop- 
per to 100 of tin ; that the second layer, being of a harsher 
nature, has 5 pounds of lead added to an 100 of the tin ; 
and that the lowest layer is mixed with 9 pounds of lead 
to an hundred of the tin ; the whole is then re-melted, 
and cooled quickly, and this, they say, is the ordinary tin 
of England ; and Geoffroij had formerly given much the 
same account.* There is, probably, no other founda- 
tion for this report, but that pewter has been mistaken for 
tin, these metals being sometimes called by the same 
name ; and fine pewter being sometimes made from a 
tnixture of 1 part of copper with 20 or 30 parts of tin. 
The mixture generally used for the tinning of copper 
vessels, consists of 3 pounds of lead, and of 5 pounds of 
pewter ; when a finer composition is required, ten parts 
of lead are mixed with sixteen of tin ; or one part of lead 
with two of tin ; but the proportions in which lead and 
tin are mixed together, even for the same kind of work, 
are not every where the same ; different artists having dif- 
ferent customs. Vessels tinned with pure tin, or with 
the best kind of pewter, which contains no lead, do not 
stain the fingers when rubbed with them : whilst those 
which are tinned with a composition, into which lead en- 
ters- as a constituent part, colour the fingers with a black- 
ish tinge. 
— - fusores aperto furni ostiolo, metallum in formas quasdam 
ex arena paratas diffluere sinunt, ibique in snassas grandiores con- 
crescit. Superior stanneae ma#sse pars adeo mollis est et flexiiis 
ut sola elaborari nequeat sine cupri miscela, trium scilicet librarum 
super stanni libras centum. Massae pars media binas tantum cu- 
pri libras recipit. Infima vero adeo fragilis est et intractabilis, 
ut cum hujus metalli centum libris plumbi libras octodecim con- 
sociare oporteat Geoff. Mat. Med. vol. X, p. 28 £» 
