EXAMPLES OF TERRACES. 259 
where the whole stream was tilted in one direction, but the resulting forms would 
be similar in appearance. They could be distinguished from climatic terraces only 
by means of a careful study of their height at many places and of the irrelatiou to 
uplifted areas and to the mountains along the course of the stream. There is, 
however, one respect in which the Heri Rud affords a valuable clue to the origin of 
the terraces. Closely associated with the river, and in one case forming part of its 
system, are some small lakes showing phenomena which it seems impossible to 
explain on any hypothesis except that of climatic change. If a study of these 
shall show the terraces of the Heri Rud to be of climatic origin, there is a strong 
presumption that the terraces of the neighboring streams are due to the same cause. 
In its lower course the Heri Rud closely resembles the Murg-ab. At Tejen 
it flows upon the surface of the plain and is also liable to the extraordinary- floods 
described in Profes.sor Davis's report. At Serakhs the cross-section is much like that 
of the Murg-ab at Hindu Kush, with the river flowing in a deep channel about 10 
feet below what may be termed either a lower terrace or an elevated flood-plain, and 
with a second terrace 20 feet high rising to a broad alluvial plain. Fifty miles 
fiirther upstream, at Pul-i-Khatun, below the lower gorge, there are four terraces. 
The lower one is small, as usual ; the second forms a broad plain half a mile wide, 
on which is located a Russian military- post to guard the only bridge in this part of 
the countr)-; the third is narrow, though distinct; and the fourth is the rather flat 
tops of the surrounding hills of old alluvium. But little was seen of the 35 miles 
of the river between Pul-i-Khatun and Zulfagar (Zulfikar) at the northwestern 
comer of Afghanistan. Most of the way the ri\-er flows in a narrow gorge, and 
whatever terraces may have existed are naturally destroyed for the most part. Just 
south of Pul-i-Khatun, in a relativeh' open stretch, two were noted, composed of 
gravel which had clearly been brought in as a filling after the work of valley- 
making had reached practically its present stage. 
At Zulfagar, in the ancient lake basin of Zorabad, the valley of the Heri Rud 
again widens, and at once the number of terraces increases. In one side valley five 
terraces were noted cut in the ancient lake clays ; in two or three others the number 
is four, while in many cases there has been so much undercutting or change of some 
sort that onh- the minimum number of two is preser\-ed. Along the main ri\-er the 
terraces, where best preserved, number five, of which the first, tliird, and fifth are 
usually strong, while the second and fourth are weak or missing. Some 10 miles 
south of the Afghan boundary and a little upstream from the dam of Dat Mehemet 
Khan, a very significant section is .seen on the right bank of the river as one looks 
downstream from the cultivated fields east of Khatami, on the left side of tlie river 
(fig. 157). Here the gravel renniants of what seem to be the third and fourth ter- 
races, counting from below upward, are seen to lie on a slope of westward-dipping 
shales which must have been subjected to erosion. The\- indicate that before the 
formation of each terrace the valle\- must have been cut well below the level of that 
teixace, though not necessarily to the present depth, and then filled with gravel. 
This is not absolutely inconsistent with a tectonic origin of the terraces, but inas- 
much as this section lies close to what nuist have been the axis of any supptosed 
