GEOLOGICAL HISTORY OF NORTHEASTERN PERSIA. 237 
THE BINALUD RANGE AND THK NEIGHBORING BASINS. 
Little is known of the third and fonrth divisions of Khorasan. I have seen 
nothing of the basins and shall not attempt to describe them. The Binalud 
^Mountains, as seen from the north, present somewliat the same \ontliful ajjpearance 
as Kopet Dagh, though to a less degree. I was told by Mr. Clemenson, of Meshed, 
that some of the valleys are as deep and narrow as those of the northern range. 
Farther south, however, the youthful outlines are lost and the mountains assume a 
mature appearance. The component rocks also change in character and become 
largely igneous or of Paleozoic age. It appears that the uplifting of the mountains 
of Eastern Persia has proceeded gradualh- from south to north. On the edge of the 
Dasht-i-Kavir the mountains are mature, farther north in the Binalud range they are 
young, while still farther north in Kopet Dagh many features are exceedingly }-oung. 
In Central Asia the same thing seems to be taking place. Step by step the ranges 
are gaining in area at the expense of the basins, and the mountainous areas of the 
central massif of Asia seem to be encroaching northward upon the great plains. 
THE .\FGH.\N DEPRESSION. 
THE HERI RUD VALLEY. 
The Afghan depression is bounded on the north by the low mountains through 
which the Heri Rud has cut its way out from the basin of Iran, (iatheriug its 
waters from the snowy heights of Hindu Kush, in the most inaccessible portion of 
northern Afghanistan, the Heri Rud flows westward for 300 miles between towering 
mountain ranges which gradually decrease in height and finally come to an end 
at the edge of the Afghan depression. Here the Heri Rud turns abruptly north, 
and after threading its way through a gorge emerges upon the plain of Transcaspia. 
There, after receiving the waters of the Keshef Rud from Meshed, it takes the name of 
Tejeu River, and soon loses itself in the swamps and sands of the Turkoman desert. 
Where the Heri Rud crosses the mountains, the eastern portion of the northern 
border of Iran appears to be offset to the south. The Paropamisus appears to be 
the continuation of Kopet Dagh, and the mountains south of Herat the continua- 
tion of the Binalud range. The eastern mountains lie roughly 50 miles south of 
their Persian counterparts. This break between the ranges of Persia and Afghan- 
istan causes the depression through which the Heri Rud escapes to the north. 
Little is known of the mountains which border the depression. Those on the 
west at the end of Kopet Dagh, according to Mushketoff, consist for the most part 
of Cretaceous limestone, but I saw several large basins and other areas where the 
prevailing fonnations are of Tertiar)- age. The topograph)- on the whole is mature ; 
it probably corresponds to that which would exist farther west in the neighborhood 
of Meshed and .\skhabad if no recent uplift had taken place. East of the river 
the topography is still more mature. Holdich (p. 113), whose opportunities for 
observation were extensi\e, describes the country north of Herat as so mature that, 
although the passes rise to a height of 4,800 feet, wagons can be driven across the 
mountains in spite of the absence of roads. In the region about 60 miles north 
of Herat, which Mushketoflf crroueouslv, I think, marks as Triassic, Holdich 
