CAUCASUS, a vast chain of mountains extending across that isthmus of Western Asia which is bounded by the Black Sea on the west and by the Caspian on the east. Commencing near the mouth of the river Kouba, which falls into the Euxine, it proceeds in a south-easterly direction, gradually increasing its distance from that sea, and then turning towards the east traverses Mingrelia and Imetria. Approaching the source of the river Kouma, a ridge diverging to the south enters Georgia near the origin of the Kur, which rises in the mountains of Kars, while the main chain, advancing to the western shores of the Caspian, proceeds through the provinces of Daghestan and Shirvan, once belonging to Persia, but now nominally under the government of Russia. Here penetrating Ghilan, it is connected in a continued chain by the mountains of Mazanderan and the Paropamisan with the Hindu Koh or Indian Caucasus, a part of the great Himalaya range. Finally, taking a south-eastern direction, it terminates at the peninsula of Apsheron, which runs out into the Caspian Sea. It is also connected by means of a secondary range near the Black Sea with the mountains of Ararat; while the spurs which are thrown out from the main ridge towards the north are gradually lost in the immense steppes of southern Russia. The length of the whole chain from the mouth of the river Kouba to the peninsula where it terminates, is estimated at from 650 to 700 miles. The breadth from Mosdok to Tiflis is computed at 180 miles; but, with its various parallel chains and ramifications, the average cannot exceed 140 miles.