78 NATURAL HISTORY OF 



there are only three rivers of importance that reach 

 the sea. They all unite into one channel ; and although 

 they drain an immense surface, generally arid and 

 sandy, and the Tigris, in particular, is swift, they have 

 no period of inundation like the Nile, but simply 

 freshes in the spring ; and albeit they terminate at the 

 head of an enclosed gulf, they have not formed an ex- 

 tensive delta. The high table land of Persia is esti- 

 mated at little less than 4000 feet above the sea, a most 

 arid desert, but with rivers from the north-eastward, 

 forming the fertile valley of the Helmund, and termi- 

 nating in Lake Aria or Zurra, anciently much more 

 extensive than the present, having ruins of vast cities 

 in the vicinity, unknown in history and of the remo- 

 test period ; the cradle where Iranian power was nur- 

 sed. From the social systems first evolved on the Oxus 

 and the Helmund, and thence carried to the Tigris, 

 Euphrates, and Choaspes, when combined with those 

 of Egypt and Palestine, the present religious, moral, 

 and scientific state of the world, is almost entirely 

 drawn. The fundamental principles relating to the 

 highest good, and the maxims of the greatest evil, 

 emanated from Western Asia, wherein the ancients 

 used to comprehend the Nile, as far up tho course of 

 tne river as the Nubian frontier. 



