350 On the Manufacture of Tin-plate. 
But what is more relevant to the subject of 
this paper, is the chemical affinity which sub- 
sists between tinand iron. One of the strong- 
est proofs of this affinity is derived from 
the circumstance that even cast-iron may be 
tinned in the same manner as wrought-iron. 
Of late years, cast-iron saucepans, and pots 
of a large size, are permanently tinned on 
their inner surfaces, to prevent the liquors 
which are boiled in them from acquiring any 
stain by a partial dissolution of the iron. 
Many other articles, such as bridle- bits, com- 
mon stirrups, small nails, &c. are now made 
much cheaper than formerly, by first fabri- 
cating them in cast-iron, and then covering 
them with a thin coat of tin, by the immer- 
sion of them in a hot mass of that fluid 
metal. | . 
That these effects are owing to chemical 
affinity, cannot be doubted, when it is con- 
sidered, that in all these cases the pores of 
the iron are in some degree actually penetra- 
ted by the tin. 
In the manufacture of tin-plate, which I 
am now about to describe, a similar effect 
is produced, and also by the same means. 
Plates of iron properly prepared, are immer- 
sed in a large mass of melted tin, which is 
he 
kept hot by a fire constantly burning under- 
