854 KETROSPECT OP THE PRINCIPAL EPOCHS 



cannot be determined by him who, with a just mistrust of 

 his remaining powers, knows only that the type of so great 

 an undertaking has floated in clear, though general, outlines 

 before his mental eye. 



In the early part of the section occupied by the epoch of 

 the Arabians, in beginning to describe the powerful influence 

 exerted by the blending of a foreign element with European 

 civilisation, I determined the period from which the history of 

 the Cosmos becomes coincident with that of the physical sci- 

 ences. According to my conception, an historical view of the 

 gradual extension of natural knowledge, both in its terrestrial 

 and celestial sphere?, is connected with definite epochs, or with 

 certain events which have exerted a powerful intellectual influ- 

 ence within definite geographical limits, and which impart to 

 those epochs their peculiar character and colouring. Such were 

 the enterprises which conducted the Greeks into the Euxine, 

 and led them to anticipate the existence of another sea shore 

 beyond the Phasis, the expeditions to the tropical lands 

 which furnished gold and incense ; the passage through 

 the Western Straits into the Atlantic Ocean, and the opening 

 of that great maritime highway of nations on which were 

 discovered at widely separated intervals of time, Cerne and 

 the Hesperides, the Northern Tin and Amber Islands, the 

 Volcanic Azores, and the New Continent of Columbus south 

 of the ancient Scandinavian settlements. The movements 

 which proceeded from the basin of the Mediterranean, and 

 from the northern extremity of the neighbouring Arabian 

 Gulf, and the voyages to the Euxine and to Ophir, are 

 followed in my historic description by the military expedi- 

 tions of the Macedonian conqueror, and his attempt to fuse 

 together the nations of the "West and of the East, by the 



