The Siwalik is a Sub-Himalayan range of the later or tertiary formation, named from Siva, a Hindu deity. What is strictly called the Siwalik extends in a north-western direction from the right bank of the Gangeki, and runs parallel to the Himalayan range, forming the boundary of the Doab between the Ganges and J1111311a ' • beyond this it skirts the Ambala and Ludhiana districts,. and comes to its termination in the Hoshiarpur district. Though this portion alone, restrictedly, receives the name of Siwalik, Dr. Boyle had shown that hills of a precisely similar nature can be traced 'all along below the Himalaya from the Indus, as far as the foot of the Sikkim Hills. The Siwaliks are merely the detritus of the Himalaya, and seldom reach 3000 feet, while the Himalaya rise nearly to 30,000 feet. At Hardwar the Siwalik Hills form the gorge at which the Ganges issues into the plains of Hindustan. The breadth of this range is at its widest part about ten miles when it approaches the Sutlej river, and towards its termination beyond that river the range assumes the form of little more than eandhills. The highest part of the range is about Hardwar ; and to the south of Garhwal, beyond Sirmur, some of the peaks are as high as 3000 or 3300 feet above the sea-level. Dr. Falconer, on his first visit to the Siwalik Hills, inferred that they were of a tertiary age, and analogous to the molasse of Switzerland. Subsequent research by other geologists has not altered that determination, although the exact knowledge of the formation has been greatly extended. About the end of 1834, Lieutenants Baker and Durand discovered the great fossiliferous deposit of the Siwalik, near the valley of Markanda, westward of the Jumna, and below Nahun. The range is all alluvial, in many places consisting of beds of gravel and rolled stones, fragments of the older formations of the Himalayan range above, consisting of granites, limestone, clayslate, gneiss, mica-schists, etc. Besides these there are beds of loose-grained sandstone, with much mica interposing. There are also beds of calcareous conglomerate and sub ordinate beds of clay. It is the clay and sand-beds of these ranges that are fossiliferous. Shells of the tertiary miocene period abound, but the chief characteristic fossils are the remains of gigantic mammalia, among which may be mentioned the Sivatherium, a huge creature somewhat similar to the tapir of modern days.
Two ranges cross the base of the Peninsula from east to west, the Vindhya north of the Nerbadda, the Satpura to the south of that river. The Vindhya rise abruptly from the Nerbadda, and the Salamber ranges on the slopes from the Malwa plateau connect the Viudhya with the Aravalli.
The Satpura range runs between the Nerbadda and the Tapti, and on its eastern edge is the Amarkantak plateau, rising 4500 feet. A moun tainous plateau, in continuation of the Satpura, extends as far as the Ganges, terminating there in the Rajmahal Hills. This ffigh land is bounded by the Sone on its N.W. face, and is divided by the river from the Kymore range. The S.E. slope of the plateau is towards the Bay of Bengal, and it is drained by the Mahanadi, Brahmany, Byturni, Sabunreka, and Damuda rivers.
The Aravalli chain of hills is connected by lower ranges with the western extremity of the Vindhya mountains on the borders of Gujerat, and stretches from S.W. to N.E. up to a considerable distance
beyond Ajmir, in the direction of Dehli. The range divides Rajputana into two nearly equal parts, forming the division between the desert on the west and the Malwa table-land. It would be more correct to say the level of the desert, for the south-eastern portion, including Jodhpur, is a fertile country. The Aravalli chain divides the tributaries of the Indus from those of the Ganges, and may hence be regarded as a continuation of the Cis-Sutlej chain of the Himalaya, which terminates to all appearance in the plains near Nahun in Sirmur. In like manlier, the peninsula of Kattyawar may be considered as the southern termination of the Aravalli, though separated from it by an alluvial plain, being the continuation of the watershed, and dividing the streams flowing to the Gulf of Cutch or the delta of the Indus from those that flow into the Gulf of Cambay.
The Dehli, Shekhawati, and Kalayana series of low hills furnish the mineral wealth of Dehli, Gurgaon, and Hissar ; they appear to be spurs and offshoots of the extremity of the Aravalli range. The principal hills are the Dehli Hills, in s\ the south-west of the cli riot of the same name, and the Shekhawati Hills in Gurgaon, etc., and the Kalayana• Hill at Da yields the flexible sandstone and the grey Narnaul marble. Among the hills in the Dehli district, a white clay, supposed to be kaolin, is produced. In Gurgaon, several clays—white, red, and- yellow—and mica occur ; also hematite and ironstone, and also copper, both at Siughana and in Hissar. Balla garb yields white and red sandstones, and the mottled red and white and blackish of the new red group.
Mount Abu, says Mr. Fergusson (p. 234), rises from the desert as abruptly as an island from the ocean up to 5650 feet high, and presents on almost every side inaccessible scarps, the summit being reached only by ravines that cut into its sides. When the summit is reached, it opens out into a lovely valley six or seven miles long by two or three miles in width, with the little Nakhi Talao or Pearl Lake, and near to it, at Delwara, the Joins selected a site for their pilgrimage or tirth. During Jaina supremacy it was adorned with several temples, two of which are of white marble. The more modern of these was built by the two brothers Tejpala and Vastupala, who erected a triple temple at Girnar (A.D. 1197-1247), and for minute delicacy of carving and beauty of details it stands almost unrivalled. The other, built also by a merchant, Vimala Sah, about A.D. 1032, is simpler and bolder, and is the oldest and most complete example of a Jaina temple. It is dedi cated to Parswanatha, who is seated within.
The term Sahyjadri is applied to the entire system of the Western Ghats (q.v.) from the Tapti river to Cape Comorin. The range consists to the northward of nearly horizontal strata of basalt and similar rocks steeply scarped on the western side. The highest summits, such as Mahabales war, 4717 feet, are perfectly flat-topped, and arc undenuded remnants of a great elevated plain. The southern portion of the Sahyadri range is entirely separated by a broad gap (the Pa]ghat, q.v.), through which the railway from Madras to Beypur passes.