~Sub Himalaya or Siwaliks.~--In its lowest ridges the Himalaya drops to a height of about 5000 feet. But the traveller to any of the summer resorts in the mountains passes through a zone of lower hills interspersed sometimes with valleys or "duns." These consist of Tertiary sandstones, clays, and boulder conglomerates, the debris in fact which the Himalaya has dropped in the course of ages. To this group of hills and valleys the general name of Siwaliks is given. East of the Jhelam it includes the Nahan hills to the north of Ambala, the low hills of Kangra, Hoshyarpur, Gurdaspur, and Jammu, and the Pabbi hills in Gujrat. But it is to the west of the Jhelam that the system has its greatest extension. Practically the whole of the soil of the plains of the Attock, Rawalpindi, and Jhelam districts consists of disintegrated Siwalik sandstone, and differs widely in appearance and agricultural quality from the alluvium of the true Panjab plains. The low hills of these districts belong to the same system, but the Salt Range is only in part Siwalik. Altogether Siwalik deposits in the Panjab cover an area of 13,000 square miles. Beyond the Indus the hills of the Kohat district and a part of the Suliman range are of Tertiary age. ~The Great Panjab Plain.~--The passage from the highlands to the plains is as a rule abrupt, and the contrast between the two is extraordinary. This is true without qualification of the tract between the Jamna and the Jhelam. It is equally true of British districts west of the Jhelam and south of the Salt Range and of lines drawn from Kalabagh on the west bank of the Indus southwards to Paniala and thence north-west through the Pezu pass to the Waziristan hills. In all that vast plain, if we except the insignificant hills in the extreme south-west of the province ending to the north in the historic ridge at Delhi, some hillocks of gneiss near Tosham in Hissar, and the curious little isolated rocks at Kirana, Chiniot, and Sangla near the Chenab and Jhelam, the only eminences are petty ridges of windblown sand and the "_thehs_" or mounds which represent the accumulated debris of ancient village sites. At the end of the Jurassic period and later this great plain was part of a sea bed. Far removed as the Indian ocean now is the height above sea level of the Panjab plain east of the Jhelam is nowhere above 1000 feet. Delhi and Lahore are both just above the 700 feet line. The hills mentioned above are humble time-worn outliers of the very ancient Aravalli system, to which the hills of Rajputana belong. Kirana and Sangla were already of enormous age, when they were islands washed by the waves of the Tertiary sea. A description of the different parts of the vast Panjab plain, its great stretches of firm loam, and its tracts of sand and sand hills, which the casual observer might regard as pure desert, will be given in the paragraphs devoted to the different districts.