ALEXANDRIAN SCIENCE. 45 



trigonometry. The great armillary sphere which had been set up at 

 Alexandria according to the design of Eratosthenes proved in the hands 

 of Hipparchus the instrument of great discoveries. The representation 

 of it in the illustration on the preceding page will serve to give the 

 reader only a general notion of the instrument. It consisted of two 

 large bronze circles, the outer one fixed in the plane of the meridian, 

 and the inner movable with the former in the same plane; one of 

 these circles was divided into 360, and the other carried a pair of 

 pointers or projecting bars. Within these circles were others corre- 

 sponding with the planes of the ecliptic and the equator. 



CTESIBIUS and HERO must be named as the successors of Archimedes 

 in the mechanical sciences at Alexandria. It was they who resolved 

 all machines into the simpler elements which we still call the mecha- 

 nical powers, namely, the lever, the wheel and axle, the wedge, the screw, 

 and the pulley. Ctesibius is credited with the invention of the forcing- 

 pump ; and both invented curious hydraulic and pneumatic appara- 

 tus, such as clepsydras with moving figures, windmills, fountains, sy- 

 phons ; and contrived methods of exhausting and compressing air, not 

 apparently unlike those still employed in the air-pump and the air-gun. 



There are notices in Vitruvius and Cicero of other mechanicians, 

 astronomers, geographers, and mathematicians, belonging to the older 

 school of Alexandria, but we pass over these as less important. But 

 here we shall interrupt the history of Alexandrian science, to say a few 

 words about the science of the Romans. 



7 Great as were the Romans in war and civil polity, they had to ac- 

 knowledge the superior genius of the Greeks in art, poetry, oratory, 

 and philosophy, and they made the great Hellenic productions their 

 models in all those departments. Geometry, astronomy, and physical 

 science generally, the Romans disregarded altogether; nay, they even 

 contemned the pursuits of science as partaking of a mechanical cha- 

 racter, regarding them as beneath the dignity of a man of liberal edu- 

 cation or of high birth. Not a single great original work on philosophy 

 or science can be attributed to a Roman. Philosophy appears to have 

 attracted the attention of the Romans only as furnishing precepts for 

 the guidance or consolation of life, and we find them divided between 

 the two rival schools of the Epicureans and the Stoics. The knowledge 

 of nature interested them only from the same practical point of view, 

 if we may judge from Virgil's lines : 



Felix, qui potuit rerum cognoscere causas 

 Atque metus omnes et inexorabile fatum, 

 Subjecit pedibus strepitumque Acherontis avari. 



In the great poem of LUCRETIUS (B.C. 99 55), " De Rerum Natura," 

 we find a remarkable exposition of the philosophy of the Epicureans, 

 who had in great part adopted the physical views of Democritus, which 

 have been already adverted to. These views were developed by Lu- 



