252 Scientific Intelligence. 



extensively warped and compressed. Above them occur reddish 

 silts containing more or less sand and gypsum and warped like 

 the underlying shales, although to a less extent. In certain 

 places toward the top of the series the red strata alternate with 

 green clays. Above all lie the deposits of silt and gravel which 

 are to-day accumulating. Although these different strata show 

 varying degrees of warping along the edges of the basins, it is 

 noticeable that toward the centers they approach the horizontal 

 position. It is probable that in the centers of many of the 

 basins an uninterrupted series of strata has been deposited from 

 the time of the post-Cretaceous uplift of the country until now. 

 At first a shallow sea or large lakes probably occupied the cen- 

 tral portions of Iran and allowed the deposition of the green 

 shales. Later, as the great basin was broken into smaller basins, 

 the larger bodies of water gave place to smaller ones, and these, 

 under the influence of a dry climate, gave place to playas or 

 shallow salt lakes where the prevailing deposits were reddish 

 silts. Still the process of deepening the basins and decreasing 

 their area went on, with the result that the green shales were 

 more highly warped and the red deposits were also uplifted along 

 the borders of the basin and were exposed to erosion. Mean- 

 while the superficial deposits which now cover the plains were 

 laid down and the country assumed its present form. It is not 

 to be supposed that every basin has gone through exactly the 

 same process, or that a single process has everywhere taken place 

 at the same time. Accidents have intervened. At Zorabad the 

 damming of the Heri Rud formed a lake and greatly altered the 

 course of events. At Sistan, and probably elsewhere, a series of 

 lakes appears to have occupied the basin during the glacial 

 period. Nevertheless the general course of events was a gradual 

 progress from larger basins to smaller basins, and from sub- 

 aqueous to subaerial deposition." 



The report is well illustrated and its publication in this country 

 cannot but help correct the too great reluctance of American 

 geologists to depart, in their interpretation of the continental 

 deposits of western America, from the traditional invoking of 

 those processes which in the infancy of geology were the sole 

 known agencies of change because they are the controlling ones 

 in its birthplace. The English geologists in India and Persia 

 long ago pointed out the magnitude and characteristics of the 

 reproductive work of rivers, and of the changes going on in arid 

 regions ; and Mr. Huntington well observes that the likeness of 

 the physical history in Central Asia and the western and south- 

 western portions of the United States is now and has been in the 

 course of geological time very striking both in product and 

 process. J. b. w. 



