406 ARCHITECTURE AND MliCHANlCAL SCIENCES, 



lion of the sphere to the cylinder, and the true principles of static* 

 and hydrostatics ? What a proof of his sagacity did he gire in dis- 

 covering the quantity of silver, that was mixed along with the gold, 

 in the crown of King Hierem ; whilst he reasoned upon that prin- 

 ciple, that all bodies immersed 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 re. 

 solved the problem. He likewise invented a perpetual screw, 

 valuable on account of its being capable to overcome any resist- 

 ance ; and the screw, that still goes by his own name, used in ele- 

 vating of water. He, of himself alone, defended the city of 

 Syracuse, by opposing to the efforts of a Roman general, the re. 

 sources he found in his own genius. By means of many various 

 warlike machines, all of his own construction, he rendered Syra. 

 cuse inaccessible to the enemy. Sometimes he hurled upon their 

 land. forces stones of such an enormous size, as crushed whole 

 bodies of them at once, and put the whole army into confusion. 

 And when they retired from the walls, he still found means to 

 annoy them ; for with catapults and balistaj, he overwhelmed them 

 with arrows innumerable, and beams of a prodigious weight. If 

 their \essels 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. And when the Romans 

 thought of sheltering themselves from his pursuit, by keeping at a 

 distance from the haven, he borrowed fire from heaven, and aided 

 by his own ingenuity, wrapped them in sudden and inevitable con. 

 flagration, as we have seen in a preceding chapter. 



The superior knowledge he had in sciences, and his confidence 

 in the powers of mechanism, prompted him once to say to King 

 Hi ron, who was his patron, admirer and friend ; give me but some 

 other place to stand upon, and I'll set the earth itself in motion : 

 and when the king, amazed at what he had said, seemed to be in 

 hesitation : he gave him a striking proof of the possibility of what 



