Thus southern Baluchistan comprises four hydrographical sections. First is the long extension from Kalat, southwards, of that inconceivably wild highland country which faces the desert of Sind, the foot of which forms the Indian frontier. This is the land of the Brahui, and the flat wall of its frontier limestone barrier is one of the most remarkable features in the configuration of the whole line of Indian borderland. For the first 60 m. from the sea near Karachi the Hab river is the boundary of Sind, and here, across the enclosing desolation of outcropping ridges and intervening sand, a road may be found into Makran. But from the point where the boundary leaves the Hab to follow the Kirthar range not a break occurs (save one) in 150 m. of solid rock wall, rising many thousands of feet straight from the sandy plain. The one break, or gorge, which allows the Kej waters to pass, only forms a local gateway into a mass of impracticable hills. Secondly, to the west of this mountain wilderness, stretching upwards from the sea in a wedge form between the Brahui highlands and the group of towering peaks which enclose the Hingol river and abut on the sea at Malan, are the alluvial flats and delta of the Purali, forming the little province of Las Bela, the home of the Las Rajput. In this hot and thirsty corner of Baluchistan, ruled by the Jam or Cham, there is a fairly wide stretch of cultivation, nourished by the alluvial detritus of the Purali and well irrigated.
In a little garden to the south of the modern town of Bela (the ancient Armabel) is the tomb of Sir Robert Sandeman, who spent the best part of an energetic and active life in the making of Baluchistan.
The boundary between Baluchistan and Afghanistan, starting Western boundary. from Nushki, cuts across the Lora hamun, leaving the frontier post of Chagai to Baluchistan, and from this point to the Malik Siah Koh it is based partly on the central mountainous water-divide already referred to, and partly runs in straight lines through the desert south of the salt swamps of the Gaud-i-Zirreh. It thus passes 50 m. to the south of the Helmund, entirely shutting off that valley and the approach to Seistan between the Helmund and the Gaud-i-Zirreh (the only approach from the east in seasons of flood) from Baluchistan. But it leaves a connected line of desert route between Nushki and Seistan, which is open in all ordinary seasons, to the south, and this route has been largely developed, posts or serais having been established at intervals and wells having been dug. There is already a promising khafila traffic along it and the railway has been extended from Quetta to Nushki.
Geology. - The mountain ranges of Baluchistan consist chiefly of Cretaceous and Tertiary beds, which are thrown into a series of folds running approximately parallel to the mountain ridges. The folds are part of an extensive system arranged as if in a festoon hanging southwards between Peshawar and Mount Ararat, but with the outer folds looped up at Sibi so as to form the subsidiary festoon of the Suliman and Bugti Hills. Outside the folds lie the horizontal deposits of the Makran coast, and within them lies the stony desert of north-western Baluchistan. In the broader depressions between the mountain ridges the beds are said to be but little disturbed. Besides the Cretaceous and Tertiary beds, Jurassic rocks are known to take a considerable part in the formation of the hills of British Baluchistan. Triassic beds lie along the south side of the upper Zhob, and Fusulina limestone has also been found there. With the exception of the later Tertiary beds the deposits are mostly marine. But in the upper Cretaceous and lower Tertiary, especially in north-western Baluchistan, there is an extensive development of volcanic tuffs and conglomerates, which are probably contemporaneous with the Deccan Traps of India. Great masses of syenite and diorite were intruded during the Tertiary period, and within the curve of the folded belt a line of recent volcanic cones stretches from western Baluchistan into eastern Persia. In Baluchistan these volcanoes appear to be extinct; though the Koh-i-Tafdan, beyond the Persian frontier, still emits vapours at frequent intervals.
The lavas and ashes which form these cones are mostly andesitic. Mud "volcanoes" occur upon the Makran coast, but it is doubtful whether these are in any way connected with true volcanic agencies.
So far as is known, the mineral wealth of Baluchistan is inconsiderable. Coal has been worked in the Tertiary beds along the Harnai route to Quetta, but the seams are thin and the quality poor. A somewhat thick and viscid form of mineral oil is met with at Khattan in the Marri country; and petroleum of excellent quality has been found in the Sherani hills and probably occurs in other portions of the Suliman Range. Sulphur has long been worked on a small scale in the Koh-i-Sultan, the largest of the volcanoes of western Baluchistan.