THE BELFAST ADDRESS 155 



risible world are to be found atoms innumerable, which 

 nave never been united to form bodies, or which, if once 

 united, have been again dispersed — falling silently through 

 immeasurable intervals of time and space. As everywhere 

 throughout the All the same conditions are repeated, so 

 must the phenomena be repeated also. Above us, below 

 us, beside us, therefore, are worlds without end; and this, 

 when considered, must dissipate every thought of a de- 

 flection of the universe by the gods. The worlds come 

 and go, attracting new atoms out of limitless space, or dis- 

 persing their own particles. The reputed death of Lucre- 

 tius, which forms the basis of Mr. Tennyson's noble 

 poem, is in strict accordance with his philosophy, which 

 was severe and pure. 



§2 



Still earlier than these three philosophers, and during 

 the centuries between the first of them and the last, the 

 human intellect was active in other fields than theirs. 

 Pythagoras had founded a school of mathematics, and 

 made his experiments on the harmonic intervals. The 

 Sophists had run through their career. At Athens had 

 appeared Socrates, Plato, and Aristotle, who ruined the 

 Sophists, and whose yoke remains to some extent un- 

 broken to the present hour. Within this period also the 

 School of Alexandria was founded, Euclid wrote his "Ele- 

 ments" and made some advance in optics. Archimedes 

 had propounded the theory of the lever, and the prin- 

 ciples of hydrostatics. Astronomy was immensely enriched 

 by the discoveries of Hipparchus, who was followed by 

 the historically more celebrated Ptolemy. Anatomy had 

 been made the basis of scientific medicine; and it is said 



