The following are the chief hydrographic divisions: (1) The Kabul river and its tributaries. (2) The Indus affluents. (3) The basin of the Oxus. (4) The basin of the Helmund. (5) The basin of the Hari Rud. [Illustration: KASI KHODA DA OF ISHKASHIM _Photo, Olufsen_] The prevailing climatic conditions of Afghanistan are dryness combined with great extremes of temperature. Snow lies on the ground for three months during the year in the Kabul and Ghazni districts, while many of the peaks from the Hindu Kush to Kelat rise above the snow-line. But so much depends on elevation that Jelalabad, 2000 feet above the sea, is scarcely colder than India, while the winters on the neighbouring Kohistan uplands are as severe as those of Russia. The coldest month of the year is February, the mean minimum being 17° F. and the maximum 38° in the northern districts. The greatest cold is accompanied by an extreme lowness of temperature; during the continuation of the cold wave, which may remain for several days, the temperature varies from a mean of 12° below zero to a maximum of 17° below freezing-point. In Kabul, where the snow lies upon the ground for three months, the thermometer falls to 3° below zero and in Ghazni it sinks to 10° below zero, with a daily maximum rise of 5°. The summer heat, on the other hand, is everywhere high, especially in the Oxus region where a shade maximum of 110° to 120° is usual. At Kabul (6500 feet) the glass rises to 90° and 100° in the shade, and in Kandahar to 110°. None the less, southern Afghanistan is, on the whole, decidedly more salubrious than the fever-stricken lowland districts of Afghan Turkestan. If such is an outline of the physical and climatic conditions of Afghanistan, the ethnographic divisions no less require mention. In spite of the disappearance of the khanates and the incorporation of their territories with Kabul, strong differences of race still mark out the several peoples. The subjoined table comprises the different tribes classified according to their geographical distribution:[30]