PHYSICAL CONTEMPLATION OF THE TJXIVEKSE. 469 



mental ground of origin, and to the metamorphoses of one 

 sole element, whilst the mathematical symbolicism of the 

 Pythagoreans, and their consideration of numbers and forms, 

 disclose a philosophy of measure and harmony. The Doric- 

 Italian school, by its constant search for numerical elements, 

 and by a certain predilection for the numerical relations of 

 space and time, laid the foundation, as it were, of the subse- 

 quent development of our experimental sciences. The history 

 of the contemplation of the universe, as I interpret its limits, 

 designates not so much the frequently recurring oscillations 

 between truth and error, as the principal epochs of the gradual 

 ^approximation to more accurate views regarding terrestrial 

 forces and the planetary system. It shows us that the Py- 

 thagoreans, according to the report of Philolaus of Croton, 

 taught the progressive movement of the non-rotating earth, 

 its revolution round the focus of the world (the central fire, 

 hestia), whilst Plato and Aristotle imagined that the earth 

 neither rotated nor advanced in space, but that, fixed to one 

 central point, it merely oscillated from side to side. Hicetas 

 of Syracuse, who must, at least, have preceded Theophrastus, 

 Heraclides Ponticus, and Ecphantus, all appear to have had 

 a knowledge of the rotation of the earth on its axis; but 

 Aristarchus of Samos, and more particularly, Seleucus of 

 Babylon, who lived one hundred and fifty years after Alexan- 

 der, first arrived at the knowledge that the earth not only- 

 rotated on its own axis, but also moved round the sun as the 

 centre of the whole planetary system. And if, in the dark 

 period of the middle ages, Christian fanaticism, and the linger- 

 ing influence of the Ptolemaic school, revived a belief in the 

 immobility of the earth, and if, in the hypothesis of the Alex- 

 andrian, Cosmas Indicopleustes, the globe again assumed 

 the form of the disc of Thales, it must not be forgotten that 

 a German Cardinal, Nicholas de Cuss, was the first who had 

 the courage and the independence of mind, again to ascribe 

 to our planet, almost a hundred years before Copernicus, both 

 rotation on its axis and translation in space. After Coperni- 

 cus, the doctrines of Tycho Brahe gave a retrograde movement 

 to science, although this was only of short duration, and when 

 once a large mass of accurate observations had been collected, 

 to which Tycho Brahe himself contributed largely, a correct 

 view of the structure of the universe could, not fnil to be 



