On the Manufacture of Tin-plate. 359 
are nothing more than preparatory measures 
for the operation which is to succeed, viz. 
that of TINNING. 
For this purpose an iron pot is nearly filled 
with a mixture of block and grain tin, ina 
melted state; and a quantity of tallow or 
grease, sufficient, when melted, to cover the 
fluid metal to the thickness of four inches, 
is put to it. However, as some gentlemen 
may not be acquainted with the difference 
between block and grain tin, it may be re- 
marked, before we proceed, that the metal 
known in commerce by the name of block 
tin, is prepared either from the mineral call- 
ed tin-stone, or the one known in Cornwall 
by the name of tin-pyrites, whilst the article 
called grain tin is smelted from an ore which 
is found in grains called stream tin ore, under 
beds of alluvial soil, in low situations, whi- 
ther in the course of ages, it has been washed 
from the hills by a succession of torrents of 
rain. The former, which is produced in the 
greatest abundance, is always contaminated 
with a portion of iron, sulphur, and other 
injurious substances, and is therefore only 
employed for common purposes—while the 
grain tin, which is nearly free from every 
impurity, and usually from twenty to thirty 
shillings per hundred weight dearer, is used 
