A HISTORY OF SCIENCE 



ilization extending unbroken throughout a period of 

 about four thousand years; the actual period is in all 

 probability twice or thrice that. Naturally enough, 

 the current of history is not an unbroken stream 

 throughout this long epoch. It appears that at least 

 two utterly different ethnic elements are involved. A 

 preponderance of evidence seems to show that the 

 earliest civilized inhabitants of Mesopotamia were not 

 Semitic, but an alien race, which is now commonly 

 spoken of as Sumerian. This people, of whom we 

 catch glimpses chiefly through the records of its suc- 

 cessors, appears to have been subjugated or over- 

 thrown by Semitic invaders, who, coming perhaps 

 from Arabia (their origin is in dispute), took possession 

 of the region of the Tigris and Euphrates, learned 

 from the Sumerians many of the useful arts, and, 

 partly perhaps because of their mixed lineage, were 

 enabled to develop the most wonderful civilization 

 of antiquity. Could we analyze the details of this 

 civilization from its earliest to its latest period we 

 should of course find the same changes which always 

 attend racial progress and decay. We should then 

 be able, no doubt, to speak of certain golden epochs 

 and their periods of decline. To a certain meagre 

 extent we are able to do this now. We know, for ex- 

 ample, that King Khammurabi, who lived about 2200 

 B.C., was a great law-giver, the ancient prototype of 

 Justinian; and the epochs of such Assyrian kings as 

 Sargon II., Asshurnazirpal, Sennacherib, and Asshur- 

 banapal stand out with much distinctness. Yet, as a 

 whole, the record does not enable us to trace with 

 clearness the progress of scientific thought. At best 



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