.
The indentations made by the type in printing the pages of this
magazine, are taken out, and the sheet rendered smooth again, by
hydraulic presses exerting a force of _twelve_ hundred tons. This would
make it necessary for us to carry up our imaginary block of granite _a
hundred feet higher_ than the Bunker Hill Monument to get a load for
them.[6]

In Mr. Francis's presses, the dies between which the sheets of iron or
copper are pressed; are directly above the four cylinders which we have
described, as will be seen by referring once more to the drawing. The
upper die is fixed--being firmly attached to the top of the frame, and
held securely down by the rows of iron pillars on the two sides, and by
the massive iron caps, called platens, which may be seen passing across
at the top, from pillar to pillar. These caps are held by large iron
nuts which are screwed down over the ends of the pillars above. The
lower die is movable. It is attached by massive iron work to the ends of
the piston-rods, and of course it rises when the pistons are driven
upward by the pressure of the water. The plate of metal, when the dies
approach each other, is bent and drawn into the intended shape by the
force of the pressure, receiving not only the corrugations which are
designed to stiffen it, but also the general shaping necessary, in
respect to swell and curvature, to give it the proper form for the side,
or the portion of a side, of a boat.

It is obviously necessary that these dies should fit each other in a
very accurate manner, so as to compress the iron equally in every part.
To make them fit thus exactly, massive as they are in magnitude, and
irregular in form, is a work of immense labor. They are first cast as
nearly as possible to the form intended, but as such castings always
warp more or less in cooling, there is a great deal of fitting afterward
required, to make them come rightly together. This could easily be done
by machinery if the surfaces were square, or cylindrical, or of any
other mathematical form to which the working of machinery could be
adapted. But the curved and winding surfaces which form the hull of a
boat or vessel, smooth and flowing as they are, and controlled, too, by
established and well-known laws, bid defiance to all the attempts of
mere mechanical motion to follow them. The superfluous iron, therefore,
of these dies, must all be cut away by chisels driven by a hammer held
in the hand; and so great is th