The highlands of Oman may be divided into three districts; _Ja’alan_ from Jebel Saffan to Jebel Fatlah on the east. _Oman_ proper on the Jebel Achdar, and _Ez-Zahirah_ on the eastern slopes of Jebel Okdat. The most populous and fertile district is that of Jebel Achdar which is also the best known. The fertility of the whole region is wonderful and in striking contrast with the barren rocks of so large a part of the coast. With a semi-tropical climate, an elevation of 3,000 to 5,000 feet and abundant springs the wadys and oases of Oman have awakened the delight and amazement of every traveller who has ventured to explore them. Water, the one priceless treasure in all Arabia, here issues in perennial streams from many rocky clefts and is most carefully husbanded by the ingenuity of the people, for wide irrigation, by means of canals or watercourses called _faluj_. Wellsted thus describes these underground aqueducts: “They are as far as I know peculiar to this country, and are made at an expense of labor and skill more Chinese than Arabian. The greater part of the surface of the land being destitute of running streams on the surface, the Arabs have sought in elevated places for springs or fountains beneath it. A channel from this fountain-head is then, with a very slight descent, bored in the direction in which it is to be conveyed, leaving apertures at regular distances to afford light and air to those who are occasionally sent to keep it clean. In this way the water is frequently conducted for a distance of six or eight miles, and an unlimited supply is thus obtained. These channels are about four feet broad and two feet deep and contain a clear, rapid stream. Most of the large towns or oases have four or five of these rivulets or _falj_ (plural _faluj_) running into them. The isolated spots to which water is thus conveyed, possess a soil so fertile that nearly every grain, fruit or vegetable, common to India, Arab or Persia, is produced almost spontaneously; and the tales of the oases will be no longer regarded as an exaggeration, since a single step conveys the traveller from the glare and sand of the desert into a fertile tract, watered by a hundred rills, teeming with the most luxurious vegetation.”