40 HISTORY OF SCIENCE. 



which in various ways he rendered to Hiero, the King of Syracuse, 

 that his name has become so celebrated. There are writings ot Archi- 

 medes still extant, which show that he must also be considered one of 

 the greatest mathematicians of ancient times; and of certain branches 

 of physical science Archimedes had a real experimental knowledge, 

 so that some fundamental principles which he first announced remain 

 as important truths to this day. But that which is most remarkable 

 in the achievements of Archimedes is the notion of applying ^science. 

 The ancient geometricians considered the application oi"their science 

 to the purpose of practical life a degradation to its dignity, and a sur- 

 render of its proud claims to ideal pre-eminence. It was therefore a 

 new departure for human progress when the lofty abstractions of geo- 

 metry came to aid the mechanical arts of every-day life. In the present 

 .day applications of scientific theory have come to be so much regarded 

 as matters of course, that we forget that it was only by one of -those 

 great leaps of thought, so characteristic of genius, that two provinces 

 of human activity which at one period seemed so remote and distinct 

 as abstract science and practical life, were brought first into contact 

 and into relations of mutual helpfulness. 



We read of Archimedes taking part in designing a huge ship, in 

 which he introduced the then novel plan of erecting three lofty masts. 

 It is related that at the launching of this ship Archimedes displayed 

 the power of the lever by using it for urging the ship off the stocks, 

 and that in reply to King Hiero's expression of wonder at the great 

 force thus excited, Archimedes uttered his famous boast, " Give me 

 but a place to stand on, and I could thus move the earth." Archi- 

 medes is considered the first who established statics and dynamics on 

 true principles. His statics rests on the notion of the centre of gravity, 

 of which he is the author. By its help, and that of certain incontest- 

 able truths, he demonstrates the principle of the reciprocity of the 

 weights and distances from the fulcrum of the lever and balance with 

 unequal arms. He also determines the position of the centre of gravity 

 in various figures, and his investigation of that of the parabola is worthy 

 of his genius, showing as it does that his researches in this direction 

 were certainly not stopped by difficulties. Archimedes devised cata- 

 pults and other warlike engines, and the story of his setting tire at the 



siege of Syracuse to the Roman ships of war, by means of mirrors 

 concentrating the rays of the noonday sun, has in it nothing impro- 

 bable. An eminent French naturalist, about the middle of the last 

 century, demonstrated the possibility of this feat by means of a number 

 of plane mirrors suitably arranged, with which he was able to set wood 

 on fire at the distance of one hundred and fifty paces. We may at 

 least infer, from the story of there being mirrors, that Archimedes had 

 made experiments involving some knowledge of the laws of optics. 



The acquaintance which Archimedes possessed with the mechanics 

 of liquids may be illustrated by the contrivance which is still called 



