CAUCASUS. Although a great number of mountain streams have their origin in the Caucasus, most of them are only insignificant tributaries by which the principal rivers are fed. The Kur, anciently the Cyrus, which takes its rise in the mountains of Kars, and directs its course through the middle of Georgia to the Caspian Sea, is the largest of the Transcaucasian rivers. From the northern declivity of the Caucasian range, the Terek, rising at the foot of Mount Kasbek, and rushing through the pass of Dariel, proceeds to the same destination. The Kouba which has its origin in the marshes on the north-western declivity of the Elburz, after sending two branches to the Sea of Azof, falls into the Black Sea. Along the Kouba, the Malka, and the Terek, is that great line of forts and Cossack stations extending almost without interruption from the Caspian to the Black Sea. The climate of the Caucasian countries, although generally speaking salubrious, is very various. The mountain tops covered with snow may be seen from valleys, gardens, and orchards, in which the most beautiful flowers and the richest fruits are growing. Into some districts, such as Imeritia and the neighbourhood of Derbend, the stranger who is unaccustomed to the peculiar nature of the climate cannot enter without great risk. The natives of the districts bordering upon the Black and Caspian Seas frequently suffer from severe fevers caused by their exposure to the pestilential exhalations rising from their marshy banks, and the unhealthy sea winds and mists which often prevail. Georgia, Mingrelia, Abasia, and the north of Daghestan, are all said to possess an excellent climate. In many parts the inhabitants of the plains are compelled to take refuge in the mountains during the heat of summer, while the mountaineers during the severity of winter descend with their flocks to the valleys. The vegetation of these regions, which differs in no respect from that usually seen in the two temperate zones, is at once various and abundant. Immense forests of pine and fir, often reaching an elevation of nearly 8000 feet, crown the mountain heights. The declivities and valleys are distributed into orchards, vineyards, corn fields, and pastures in rich variety. Grapes, chestnuts, figs, peaches, as well as grain of every description, rice, cotton, hemp, &c., grow in great abundance all over the country. The fruit trees generally attain a height and thickness which astonish the traveller from the most fertile regions of Europe. Among the natural productions of the Caucasus may be mentioned nitrate of potash, mineral pitch, and the hot sulphur springs which are found in different parts of it. The Ghebers, or fire worshippers, still perform the ceremonies of their faith in presence of the "eternal fires," which burn on the peninsula of Apsheron. These fires are not produced, as described in the works of earlier travellers, by the naphtha with which the soil is impregnated, but, according to M. Eichwald of Wilna, "by hydrogen gas (probably carburetted hydrogen) which rises through cracks and openings of the calcareous rocks, and on the approach of a flame takes fire, and continues to burn. It never takes fire spontaneously, nor by the approach of red coal, if not burning with flame. The gas, as it escapes from the rock, is without smell—is not sensibly warm—and on being respired does not occasion any disagreeable feeling. It burns with a yellowish-white flame, and forms with atmospheric air an exploding gas."