It is evident that the perfection of this mode of
printing depends in a great measure on finding some soft
substance like leather, which will take as much ink as it ought
from the block, and which will give it up most completely to
paper. Impressions thus obtained are usually fainter on the lower
side; and in order in some measure to remedy this defect, rather
more ink is put on the block at the first than at the second
impression.
Of copying by casting
105. The art of casting, by pouring substances in a fluid
state into a mould which retains them until they become solid, is
essentially an art of copying; the form of the thing produced
depending entirely upon that of the pattern from which it was
formed.
106. Of casting iron and other metals.--Patterns of wood or
metal made from drawings are the originals from which the moulds
for casting are made: so that, in fact, the casting itself is a
copy of the mould; and the mould is a copy of the pattern. In
castings of iron and metals for the coarser purposes, and, if
they are afterwards to be worked even for the finer machines,
the exact resemblance amongst the things produced, which takes
place in many of the arts to which we have alluded, is not
effected in the first instance, nor is this necessary.
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