By JOHN TIMBS, F.S.A.
(287-212 B.C.)
[Illustration: A boat. [TN]]
It is scarcely possible to view the vast steamships of our day without
reflecting that to a great master of mechanics, upward of two thousand
years since, we in part owe the invention of the machine by which these
mighty vessels are propelled upon the wide world of waters. This power
is an application of "the Screw of Archimedes," the most celebrated of
the Greek geometricians. He was born in Sicily, in the Corinthian colony
of Syracuse, in the year 287 B.C., and when a very young man, was
fortunate enough to enjoy the patronage of his relative Hiero, the
reigning prince of Syracuse.
The ancients attribute to Archimedes more than forty mechanical
inventions--among which are the endless screw; the combination of
pulleys; an hydraulic organ, according to Tertullian; a machine called
the HELIX, or screw, for launching ships; and a machine called
_loculus_, which appears to have consisted of forty pieces, by the
putting together of which various objects could be framed, and which
were used by boys as a sort of artificial memory.
Archimedes is said to have obtained the friendship and confidence of
Hiero by the following incident. The king had delivered a certain weight
of gold to a workman, to be made into a crown. When the crown was made
and sent to the king, a suspicion arose in the royal mind that the gold
had been adulterated by the alloy of a baser metal, and he applied to
Archimedes for his assistance in detecting the imposture; the difficulty
was to measure the bulk of the crown without melting it into a regular
figure; for silver being, weight for weight, of greater bulk than gold,
any alloy of the former in place of an equal weight of the latter would
necessarily increase the bulk of the crown; and at that time there was
no known means of testing the purity of metal. Archimedes, after many
unsuccessful attempts, was about to abandon the subject altogether, when
the following circumstance suggested to his discerning and prepared mind
a train of thought which led to the solution of the difficulty. Stepping
into his bath one day, as was his custom, his mind doubtless fixed on
the object of his research, he chanced to observe that, the bath being
full, a quantity of water of the same bulk as his body must flow over
before he could immerse himself. He probably perceived that any other
body of the same bulk would have raised the water equally; but that
another body of the same weight, but less bulky, would not have produced
so great an effect. In the words of Vitruvius, "as soon as he had hit
upon this method of detection, he did not wait a moment, but jumped
joyfully out of the bath, and running forthwith toward his own house,
called out with a loud voice that he had found what he sought. For as he
ran he called out, in Greek, 'Eureka! Eureka!--I have found it! I have
found it!'" When his emotion had sobered down, he proceeded to
investigate the subject calmly. He procured two masses of metal, each of
equal weight with the crown--one of gold and the other of silver--and
having filled a vessel very accurately with water, he plunged into it
the silver, and marked the exact quantity of water that overflowed. He
then treated the gold in the same manner, and observed that a less
quantity of water overflowed than before. He next plunged the crown into
the same vessel full of water, and observed that it displaced more of
the fluid than the gold had done, and less than the silver; by which he
inferred that the crown was neither pure gold nor pure silver, but a
mixture of both. Hiero was so gratified with this result as to declare
that from that moment he could never refuse to believe anything
Archimedes told him.
Travelling in Egypt, and observing the necessity of raising the water of
the Nile to points which the river did not reach, as well as the
difficulty of clearing the land from the periodical overflowings of the
Nile, Archimedes invented for this purpose the screw which bears his
name. It was likewise used as a pump to clear water from the holds of
vessels; and the name of Archimedes was held in great veneration by
seamen on this account. The screw may be briefly described as a long
spiral with its lower extremity immersed in the water, which, rising
along the channels by the revolution of the machine on its axis, is
discharged at the upper extremity. When applied to the propulsion of
steam-vessels the screw is horizontal; and being put in motion by a
steam-engine, drives the water backward, when its reaction, or return,
propels the vessel.
The mechanical ingenuity of Archimedes was next displayed in the various
machines which he constructed for the defence of Syracuse during a three
years' siege by the Romans. Among these inventions were catapults for
throwing arrows, and ballistae for throwing masses of stone; and iron
hands or hooks attached to chains, thrown to catch the prows of the
enemy's vessels, and then overturn them. He is likewise stated to have
set their vessels on fire by burning-glasses; this, however, rests upon
modern authority, and Archimedes is rather believed to have set the
ships on fire by machines for throwing lighted materials.
[Illustration: Death of Archimedes.]
After the storming of Syracuse, Archimedes was killed by a Roman
soldier, who did not know who he was. The soldier inquired, but the
philosopher, being intent upon a problem, begged that his diagram might
not be disturbed; upon which the soldier put him to death. At his own
request, expressed during his life, a sphere inscribed in a cylinder was
sculptured on his tomb, in memory of his discovery that the solid
contents of a sphere is exactly two-thirds of that of the circumscribing
cylinder; and by this means the memorial was afterward identified. One
hundred and fifty years after the death of Archimedes, when Cicero was
residing in Sicily, he paid homage to his forgotten tomb. "During my
quaestorship," says this illustrious Roman, "I diligently sought to
discover the sepulchre of Archimedes, which the Syracusans had
totally neglected, and suffered to be grown over with thorns and briars.
Recollecting some verses, said to be inscribed on the tomb, which
mentioned that on the top was placed a sphere with a cylinder, I looked
round me upon every object at the Agragentine Gate, the common
receptacle of the dead. At last I observed a little column which just
rose above the thorns, upon which was placed the figure of a sphere and
cylinder. This, said I to the Syracusan nobles who were with me, this
must, I think, be what I am seeking. Several persons were immediately
employed to clear away the weeds and lay open the spot. As soon as a
passage was opened, we drew near, and found on the opposite base the
inscription, with nearly half the latter part of the verses worn away.
Thus would this most famous, and formerly most learned, city of Greece
have remained a stranger to the tomb of one of its most ingenious
citizens, had it not been discovered by a man of Arpinum."
To Archimedes is attributed the apophthegm: "Give me a lever long
enough, and a prop strong enough, and with my own weight I will move the
world." This arose from his knowledge of the possible effects of
machinery; but however it might astonish a Greek of his day, it would
now be admitted to be as theoretically possible as it is practically
impossible. Archimedes would have required to move with the velocity of
a cannon-ball for millions of ages to alter the position of the earth by
the smallest part of an inch. In mathematical truth, however, the feat
is performed by every man who leaps from the ground; for he kicks the
world away when he rises, and attracts it again when he falls back.
Under the superintendence of Archimedes was also built the renowned
galley for Hiero. It was constructed to half its height, by three
hundred master workmen and their servants, in six months. Hiero then
directed that the vessel should be perfected afloat; but how to get the
vast pile into the water the builders knew not, till Archimedes invented
his engine called the helix, by which, with the assistance of very few
hands he drew the ship into the sea, where it was completed in six
months. The ship consumed wood enough to build sixty large galleys; it
had twenty tiers of bars and three decks; the middle deck had on each
side fifteen dining apartments besides other chambers, luxuriously
furnished, and floors paved with mosaics of the story of the "Iliad." On
the upper deck were gardens with arbors of ivy and vines; and here was a
temple of Venus, paved with agates, and roofed with Cyprus-wood; it was
richly adorned with pictures and statues, and furnished with couches and
drinking-vessels. Adjoining was an apartment of box-wood, with a clock
in the ceiling, in imitation of the great dial of Syracuse; and here was
a huge bath set with gems called Tauromenites. There were also on each
side of this deck, cabins for the marine soldiers, and twenty stables
for horses; in the forecastle was a fresh-water cistern which held 253
hogsheads; and near it was a large tank of sea-water, in which fish were
kept. From the ship's sides projected ovens, kitchens, mills, and other
offices, built upon beams, each supported by a carved image nine feet
high. Around the deck were eight wooden towers, from each of which was
raised a breastwork full of loopholes, whence an enemy might be annoyed
with stones each tower being guarded by four armed soldiers and two
archers. On this upper deck was also placed the machine invented by
Archimedes to fling stones of 300 pounds weight and darts eighteen feet
long, to the distance of 120 paces; while each of the three masts had
two engines for throwing stones. The ship was furnished with four
anchors of wood and eight of iron; and "the water-screw" of Archimedes,
already mentioned, was used instead of a pump for the vast ship; "by the
help of which one man might easily and speedily drain out the water,
though it were very deep." The whole ship's company consisted of an
immense multitude, there being in the forecastle alone 600 seamen. There
were placed on board her 60,000 bushels of corn, 10,000 barrels of salt
fish, and 20,000 barrels of flesh, besides the provisions for her
company. She was first called the Syracuse, but afterward the
Alexandria. The builder was Archias, the Corinthian shipwright. The
vessel appears to have been armed for war and sumptuously fitted for a
pleasure-yacht, yet was ultimately used to carry corn. The timber for
the main mast, after being in vain sought for in Italy, was brought from
England. The dimensions are not recorded, but they must have exceeded
those of any ship of the present day; indeed, Hiero, finding that none
of the surrounding harbors sufficed to receive his vast ship, loaded it
with corn and presented the vessel with its cargo to Ptolemy, King of
Egypt, and on arriving at Alexandria it was hauled ashore, and nothing
more is recorded respecting it. A most elaborate description of this
vast ship has been preserved to us by Athenaeus, and translated into
English by Burchett, in his "Naval Transactions."
Archimedes has been styled the Homer of geometry; yet it must not be
concealed that he fell into the prevailing error of the ancient
philosophers--that geometry was degraded by being employed to produce
anything useful. "It was with difficulty," says Lord Macaulay, "that he
was induced to stoop from speculation to practice. He was half ashamed
of those inventions which were the wonder of hostile nations, and always
spoke of them slightingly, as mere amusements, as trifles in which a
mathematician might be suffered to relax his mind after intense
application to the higher parts of his science."