Hipparchus was the first who calculated tables of the motion of the sun and moon, and composed a catalogue of the fixed stars. He was also the first who, from the observation of eclipses, determined the longitude of places upon earth: but his highest honour is, that he laid the first foundations for the discovery of the precession of the equinoxes.
Archimedes discovered the square of the parabola, the properties of spiral lines, the proportion of the sphere to the cylinder, and the true principles of statics and hydrostatics. His sagacity is evident from the means he adopted to discover the quantity of silver that was mixed along with the gold, in the crown of king Hieron. He reasoned upon the principle, that all bodies immerged in water lose just so much of their weight, as a quantity of water equal to them in bulk weighs. Hence he drew this consequence, that gold being more compact must lose less of its weight, and silver more; and that a mingled mass of both, must lose in proportion to the quantities mingled. Weighing therefore the crown in water and in air, and two masses, the one of gold, the other of silver, equal in weight to the crown; he thence determined what each lost of their weight, and so solved the problem. He likewise invented a perpetual screw, valuable on account of its being capable to overcome any resistance; and the screw that still goes by his own name, used in the elevating of water. He alone defended the city of Syracuse, by opposing to the efforts of the Romans the resources of his genius. By means of machines, of his own construction, he rendered Syracuse inaccessible. Sometimes he hurled upon the land forces stones of such enormous size, as crushed whole phalanxes of them at once. When they retired from the walls, he overwhelmed them with arrows innumerable, and beams of a prodigious weight, discharged from catapults and balistæ. If their vessels approached the fort, he seized them by the prows with grapples of iron, which he let down upon them from the wall, and rearing them up in the air, to the great astonishment of every body, shook them with such violence, as either to break them in pieces, or sink them to the bottom. When they kept at a distance from the haven, he focalized fire from heaven, and wrapped them in sudden and inevitable conflagration. He once said to king Hieron, “Give me but a place to stand upon, and I will move the earth.” The king was amazed by the declaration, and Archimedes gave him a specimen of his power by launching singly by himself a ship of a prodigious size. He built for the king an immense galley, of twenty banks of oars, containing spacious apartments, gardens, walks, ponds, and every convenience required by regal dignity. He constructed a sphere, representing, the motions of the stars, which Cicero esteemed one of the inventions which did the highest honour to human genius. He perfected the manner of augmenting the mechanic powers, by the multiplication of wheels and pullies; and carried mechanics so far, that his works surpass imagination.
Mechanics.
The immense machines, of astonishing force, which the ancients adapted to the purposes of war, prove their amazing proficiency in mechanics. It is difficult to conceive how they reared their bulky moving towers: some of them were a hundred and fifty-two feet in height, and sixty in compass, ascending by many stories, having at bottom a battering ram, of strength sufficient to beat down walls; in the middle, a drawbridge, to be let down upon the wall of the city attacked, afforded easy passage into the town for the assailants; and at top a body of men, placed above the besieged, harassed them without risk to themselves. An engineer at Alexandria, defending that city against the army of Julius Cæsar, by means of wheels, pumps, and other machinery, drew from the sea prodigious quantities of water, and discharged it upon the adverse army to their extreme discomfiture.
The mechanical enterprise and skill of the ancients are evidenced by their vast pyramids existing in Egypt, and the magnificent ruins of the cities of Palmyra and Balbec. Italy is filled with monuments of the greatness of ancient Rome.
Ancient Cities.
The finest cities of Europe convey no idea of the grandeur of ancient Babylon, which being fifteen leagues in circumference, was encompassed with walls two hundred feet in height, and fifty in breadth, whose sides were adorned with gardens of a prodigious extent, which arose in terraces one above another, to the very summit of the walls. For the watering of these gardens there were machines, which raised the water of the Euphrates to the highest of the terraces. The tower of Belus, arising out of the middle of the temple, was of so vast a height, that some authors have not ventured to assign its altitude; others put it at a thousand paces.
Ecbatane, the capital of Media, was eight leagues in circumference, and surrounded with seven walls in form of an amphitheatre, the battlements of which were of various colours, white, black, scarlet, blue, and orange; all of them covered with silver or with gold.