BALK, or Balkh (the ancient Bactra), formerly a great city, is now an immense and desolate mass of ruins, situated on the right bank of the Adirshah, or Balk River, in a large and fertile plain, 1800 feet above the sea. These ruins consist chiefly of fallen mosques and decayed tombs built of sun-dried bricks, and occupy a space of about twenty miles in circuit. None of these ruins are of an age prior to Mahometanism. Balk is still called by the Asiatics "Mother of Cities," but its population, which once numbered some hundred thousands, now scarcely amounts to 2000. This city is said to have been built by Kaiomurs, the founder of the Persian monarchy; and here the archi-magus resided till the followers of Zoroaster were overcome by the khalifs. Zenghis Khan sacked the city, and butchered its inhabitants; and under the house of Timour it became a province of the Mogul empire. Balk formed the government of Aurungzeb in his youth, and was at last invaded by the great Nadir. Under the Dooranee monarchy it fell into the hands of the Afghans; and for the last twenty years it has been in the possession of the Khan of Bokhara. (See Burnes's Travels in Bokhara.)