The Jamna.—The Jamna is the Yamuna of Sanskrit writers. Ptolemy's and Pliny's versions, Diamouna and Jomanes, do not deviate much from the original. It rises in the Kumáon Himálaya, and, where it first meets the frontier of the Simla Hill States, receives from the north a large tributary called the Tons. Henceforth, speaking broadly, the Jamna is the boundary of the Panjáb and the United Provinces. On the Panjáb bank are from north to south the Sirmúr State, Ambála, Karnál, Rohtak, Delhi, and Gurgáon. The river leaves the Panjáb where Gurgáon and the district of Mathra, which belongs to the United Provinces, meet, and finally falls into the Ganges at Allahábád. North of Mathra Delhi is the only important town on its banks. The Jamna is crossed by railway bridges between Delhi and Meerut and between Ambála and Saháranpur.
Changes in Rivers.—Allusion has already been made to the changes which the courses of Panjáb rivers are subject to in the plains. The Indus below Kálabágh once ran through the heart of what is now the Thal desert. We know that in 1245 A.D. Multán was in the Sind Ságar Doáb between the Indus and the united streams of the Jhelam, Chenáb, and Ráví. The Biás had then no connection with the Sutlej, but ran in a bed of its own easily to be traced to-day in the Montgomery and Multán districts, and joined the Indus between Multán and Uch. The Sutlej was still flowing in the Hakra bed. Indeed its junction with the Biás near Harike, which probably led to a complete change in the course of the Biás, seems only to have taken place within the last 150 years[2].
CHAPTER IV
GEOLOGY AND MINERAL RESOURCES
Extent of Geological Record.—Although the main part of the Panjáb plain is covered by a mantle of comparatively recent alluvium, the provinces described in this book display a more complete record of Indian geological history than any other similar area in the country. The variety is so great that no systematic or sufficient description could be attempted in a short chapter, and it is not possible, therefore, to do more in these few pages than give brief sketches of the patches of unusual interest.
Aravallí System.—In the southern and south-eastern districts of the Panjáb there are exposures of highly folded and metamorphosed rocks which belong to the most ancient formations in India. These occupy the northern end of the Aravallí hills, which form but a relic of what must have been at one time a great mountain range, stretching roughly south-south-west through Rájputána into the Bombay Presidency. The northern ribs of the Aravallí series disappear beneath alluvial cover in the Delhi district, but the rocks still underlie the plains to the west and north-west, their presence being revealed by the small promontories that peep through the alluvium near the Chenáb river, standing up as small hills near Chiniot in the Sháhpur, Jhang, and Lyallpur districts.
The Salt Range in the Jhelam and Sháhpur districts, with a western continuation in the Mianwálí district to and beyond the Indus, is the most interesting part of the Panjáb to the geologist. It contains notable records of three distinct eras in geological history. In association with the well-known beds of rock-salt, which are being extensively mined at Kheora, occur the most ancient fossiliferous formations known in India, corresponding in age with the middle and lower part of the Cambrian system of Europe. These very ancient strata immediately overlie the red marls and associated rock-salt beds, and it is possible that they have been thrust over bodily to occupy this position, as we have no parallel elsewhere for the occurrence of great masses of salt in formation older than the Cambrian.
The second fragment of geological history preserved in the Salt Range is very much younger, beginning with rocks which were formed in the later part of the Carboniferous period. The most remarkable feature in this fragment is a boulder-bed, resting unconformably on the Cambrian strata and including boulders of various shapes and sizes, which are often faceted and striated in a way indicative of glacial action. Several of the boulders belong to rocks of a peculiar and unmistakable character, such as are found in situ on the western flanks of the Aravallí Range, some 750 miles to the south. The glacial conditions which gave rise to these boulder-beds were presumably contemporaneous with those that produced the somewhat similar formation lying at the base of the great coal-bearing system in the Indian peninsula. The glacial boulder-bed thus offers indirect evidence as to the age of the Indian coal-measures, for immediately above this bed in the Salt Range there occur sandstones containing fossils which have affinities with the Upper Carboniferous formations of Australia, and on these sandstones again there lie alternations of shales and limestones containing an abundance of fossils that are characteristic of the Permo-Carboniferous rocks of Russia. These are succeeded by an apparently conformable succession of beds of still younger age, culminating in a series of shales, sandstones, and limestones of unmistakably Triassic age.
There is then an interruption in the record, and the next younger series preserved occurs in the western part of the Salt Range as well as in the hills beyond the Indus. This formation is of Upper Jurassic age, corresponding to the well-known beds of marine origin preserved in Cutch. Then follows again a gap in the record, and the next most interesting series of formations found in the Salt Range become of great importance from the economic as well as from the purely scientific point of view; these are the formations of Tertiary age.