378 
Tin. 
with wood ; it would be a problem well deserving the 
consideration of chemists, to inquire into the manner how 
a metallic covering operates in injuring the construction 
of the ships, and whether that operation is exerted on the 
iron bolts, or on the timbers of the ship.^ 
When the iron plates have been either hammered or rolled 
to a proper thickness, they are steeped in an acid liquor, 
which is produced from the fermentation of barley meal, 
though any other weak acid would answer the purpose: this 
steeping, and a subsequent scouring, cleans the surface of 
the iron from every speck of rust or blackness, the least 
of which, would hinder the tin from sticking to the iron, 
since no metal will combine itself with any earth, and rust 
is the earth of iron. After the plates have been made quite 
bright, they are put into an iron pot filled With melted 
tin ; the surface of the melted tin is kept covered with 
suet or pitch, or some fat substance, to prevent it from 
being calcined ; the tin presently unites itself to the iron, 
covering each side of every plate with a thin white coat ; 
the plates are then taken out of the melted tin, and under- 
going some further operations, which render them more 
neat and saleable, but are not essential to the purpose of 
tinning them, they are packed up in boxes, and are every 
where to be met with in commerce under the name of tin- 
plates ; though the principal part of their substance is iron, 
and hence the French have called them far blanc , or white 
iron : Sir John Pettus says, that they were with us vul- 
garly called latten ; though that word more usually I 
think denoted brass. 
Tin is not, but iron is liable to contract rust by ex- 
posure to air and moisture, and hence the chief use of 
* It is owing to the oxydation of the iron and the copper, arising 
from the galvanic action of each on the other. The bolts and nails 
should be of copper. T. C. 
