Geology. 251 



"For fifteen out of the twenty-four glaciated valleys examined 

 the first theory is sufficient, but it will not explain the other 

 nine. In eight of these nine valleys one or more of the older 

 moraines lies upon a topography different from that of to-day, so 

 as to suggest that the moraines and the floor on which they rest 

 have been trenched by a valley of stream erosion. In this valley 

 lie the younger moraines, leaving the older moraines as terraces 

 which extend beyond the later moraines both up-valley and down- 

 valley ; the up-valley extension of the morainic terrace gives a 

 minimum measure of the retreat of the glacier during the inter- 

 glacial epoch. In the ninth valley a detached portion of an older 

 moraine lies far up-valley from its successor and even above the 

 main part of the modern moraine. These facts are to be ex- 

 plained only by supposing a glacial retreat and advance in each 

 interglacial epoch, and hence a warmer interglacial epoch between 

 colder glacial epochs. Another sort of evidence of a warmer 

 interglacial epoch is found where one moraine lies upon its prede- 

 cessor in an attitude which indicates that before the deposition 

 of the younger moraine the older one was first an area of erosion 

 and later of deposition. All these facts accord with the theory 

 of successive advances and retreats, and thus warrant the division 

 of the glacial period into several glacial and interglacial epochs. 

 In one place or another signs of an interglacial retreat are found 

 between each successive pair of the four earlier moraines, while 

 the fifth moraine stands apart from the others, except at Kan Su, 

 where the time during which there is evidence of retreat may be 

 either between the third and fourth or fourth and fifth advances 

 of the ice. Everywhere the climate of the successive glacial 

 epochs seems to have grown less severe, and the duration of the 

 interglacial epochs seems to have diminished in the same ratio." 



A succession of terraces found in the valleys are regarded as 

 the result of a climatic change. The number of climatic swings 

 thus inferred agrees essentially with the series of cold epochs 

 based upon the occurrence and distribution of moraines. He 

 states : " The essential point in our study of the recent geological 

 history of Turkestan is this : From three separate lines of rea- 

 soning, based on the allied yet distinct phenomena of glaciation, 

 terracing, and lake expansion, we arrive at the same conclusion, 

 namely, that during the Quaternary era there have been a num- 

 ber of colder or glacial epochs, five or more, separated by warmer 

 interglacial epochs when the climate was similar to that of to-day; 

 and further, that these epochs progressively decreased in length 

 and intensity." 



In the final article on the basin of eastern Persia and Sistan 

 Mr. Huntington discusses briefly the geology and in a more com- 

 plete way the physiography of this desert basin. In a summary 

 paragraph he states : " The facts set forth above, so far as they 

 warrant any conclusion, suggest that in Eastern Persia the lower 

 strata of the basins are generally greenish shales, which are now 

 exposed along the edges of the basins where they have been 



