had discovered that his protege had wonderful
mechanical ingenuity, and he made good use of this discovery. Under
stress of the king's urgings, the philosopher was led to invent a great
variety of mechanical contrivances, some of them most curious ones.
Antiquity credited him with the invention of more than forty machines,
and it is these, rather than his purely mathematical discoveries, that
gave his name popular vogue both among his contemporaries and with
posterity. Every one has heard of the screw of Archimedes, through which
the paradoxical effect was produced of making water seem to flow up
hill. The best idea of this curious mechanism is obtained if one will
take in hand an ordinary corkscrew, and imagine this instrument to
be changed into a hollow tube, retaining precisely the same shape but
increased to some feet in length and to a proportionate diameter. If one
will hold the corkscrew in a slanting direction and turn it slowly to
the right, supposing that the point dips up a portion of water each time
it revolves, one can in imagination follow the flow of that portion
of water from spiral to spiral, the water always running downward, of
course, yet paradoxically being lifted higher and higher towards
the base of the corkscrew, until finally it pours out (in the actual
Archimedes' tube) at the top. There is another form of the screw in
which a revolving spiral blade operates within a cylinder, but the
principle is precisely the same. With either form water may be lifted,
by the mere turning of the screw, to any desired height. The ingenious
mechanism excited the wonder of the contemporaries of Archimedes, as
well it might. More efficient devices have superseded it in modern
times, but it still excites the admiration of all who examine it, and
its effects seem as paradoxical as ever.

Some other of the mechanisms of Archimedes have been made known to
successive generations of readers through the pages of Polybius and
Plutarch. These are the devices through which Archimedes aided King
Hiero to ward off the attacks of the Roman general Marcellus, who in the
course of the second Punic war laid siege to Syracuse.

Plutarch, in his life of Marcellus, describes the Roman's attack and
Archimedes' defence in much detail. Incidentally he tells us also how
Archimedes came to make the devices that rendered the siege so famous:

"Marcellus himself, with threescore galleys of five rowers at every
bank, well armed and full