GENERAL RETROSIECT. 353 



scidces. According to my idea, the historical recognition of 

 the gradual extension of natural science in the two spheres 

 of terrestrial and celestial knowledge (geography and astrono- 

 my) is associated Avith certain periods and certain active intel- 

 .ectual events, which impart a peculiar character and coloring to 

 :hose epochs. Such, for instance, were the undertakings which 

 led Europeans into the Euxine, and permitted them to con- 

 jecture the existence of another sea-shore beyond the Phasis ; 

 the expeditions to tropical lands rich in gold and incense ; the 

 passage through the Western Straits, or the opening of that 

 great maritime route on which were discovered, at long inter- 

 vals of time, Cerne and the Hesperides, the northern tin and 

 amber lands, the volcanic islands of the Azores, and the New 

 Continent of Columbus, south of the ancient settlement of the 

 Scandinavians. To the consideration of the movements which 

 emanated from the basin of the Mediterranean, and the most 

 northern part of tlie neighboring Arabian Gulf, and of the ex- 

 peditions on the Euxine and to Ophir,/Succeed, in my histor- 

 ical delineation, the campaigns of the Macedonian conqueror, 

 and his attempts to fuse together the west and the east ; the 

 influence exercised by Indian maritime trade and by the Alex- 

 andrian Institute under the Ptolemies ; the universal dominion 

 of the Komans under the Csesars ; and, lastly, the taste evinc- 

 ed by the Arabs for the study of nature and of natural forces, 

 especially with reference to astronomy, mathematics, and prac 

 tical chemistry, a taste that exercised so important and bene- 

 ficial an influence. According to my view, the series of events 

 which suddenly enlarged the sphere of ideas, excited a taste 

 for the investigation of physical laws, and animated the efforts 

 of men to arrive at the ultimate comprehension of the uni- 

 verse as a whole, terminated with the acquisition of an entire 

 hemisphere which had till then lain concealed, and which con- 

 stituted the greatest geographical discovery ever made. Since 

 this period, as we have already remarked, the human mind 

 has brought forth great and noble fruits without the incite- 

 ment of external occurrences, and, as the effect of its own in- 

 herent power, developed simultaneously in all directions. 



Among the instruments which man formed for himself, like 

 new organs, as it were, to heighten his powers of sensuous 

 perception, there was one which exercised an influence similar 

 to that of some great and sudden event. By the power of 

 penetrating space possessed by the telescope, considerable poi' 

 tions of the heavens were almost at once explored, the num- 

 ber of known heavenh" bodies was increased, and attempts 



