at place are not _raised_, it does not come under this
head. The massive stones which were used in the construction of some
of the ancient edifices, were evidently raised by inclined planes. A
huge mound of earth was built up round the building, completely
enclosing it; and the elevation of the mound kept pace with that of
the edifice: thus giving the laborers a chance to roll up the stones
to their places. They used no other mechanical power than the simple
windlass and lever; and no other carriage than a drag, under which was
placed rollers. When the building was completed, the earth was taken
away, and levelled about the vicinity. The modern method of raising
stones for building, and which is now used in the building of heavy
stone edifices, is by the use of a set of stout tackle blocks, the
_fall rope_ of which is taken up by a geered windlass, operated by a
steam engine; the upper block being of course attached to an elevated
_shears_ or derick. Vessels, and other bodies, which have been sunk in
the ocean, have been sometimes raised by means of airtight sacks,
attached to different parts of the object by means of diving bells,
been inflated with air, forced down through hollow tubes by pumps,
till they thus acquired a buoyancy sufficient for the purpose. The
power of buoyancy has also been applied for elevating vessels above
water, by placing hollow trunks, filled with water, under the keel of
the vessel, and then pumping them out. One of the best methods that
has ever yet been proposed for raising vessels to repair, is to place
under the keel a horizontal platform, to which is attached four large
hollow trunks under its four corners: the trunks to be filled with
water, and to have open apertures in the bottom of each. Then by
allowing a stream of atmospheric air, to rush by its own expansive
force from the reservoirs in which it had been previously compressed,
through suitable pipes or hose, into each trunk, the water is expelled
through the apertures in the bottom, and the vessel is elevated
immediately, and without loss of time. In this case, the reservoirs
(iron cylinders) of compressed air, may be recharged by steam or other
power, during the process of repairing one vessel, and be thus in
readiness for another. A patent has been granted for this invention,
but it has not yet been put in operation on a scale of practical use,
though the patentee would willingly give the right of the patent to
any person or comp