In northern Arabia the Syrian desert and the great Nafud (Nefud) have been crossed by several travellers, though a large area remains unexplored in the north-east between Kasim and the gulf.
From the wells of Shakik he crossed the waterless Nafud in four days to Jubba, and after a halt there in the nomad camps, he moved on to Hail, already a thriving town, and the capital of the Shammar state whose limits included all northern Arabia from Kasim to the Syrian border.
Nolde crossed the Nafud to Haiyania by 'a more direct track than that from Shakik to Jubba.
Sirhan is continuous with the depression known as the Jauf, situated on the northern edge of the Nefud or Nafud, and the halfway station between Damascus and Hail; and it is possible that this depression continues eastward towards the Euphrates along a line a little north of the thirtieth parallel, where wells and pasturages are known to exist.
In the spring months, when their camels are in milk, the Bedouins care nothing for water, and wander far into the Nafud with their flocks in search of the green pasture which springs up everywhere after the winter rains.
A few wells exist actually in the Nafud in the district called El Hajra, near its north-eastern border, and along its southern border, between J.
Owing to the great extent of the Nafud desert, the formation of sand-dunes is exemplified on a proportionate scale.
In many places longitudinal dunes are found exceeding a day's journey in length, the valleys between which take three or four hours to cross; but the most striking feature of the Nafud are the high crescent-shaped sand-hills, known locally as falk or falj, described by Blunt and Huber, who devoted some time to their investigation.
In the south of the Nafud, where Huber found the prevailing wind to be from the south, the falks are turned in that direction.
The general level of the Nafud was found by Huber's observations to be about 3000 ft.
Other peaks cropping out of the Nafud are Jebel Tawil, near the wells of Shakik, and J.
The surface of the harra is extremely broken, forming a labyrinth of lava crags and blocks of every size; the whole region is sterile and almost waterless, and compared with the Nafud it produces little vegetation; but it is resorted to by the Bedouin in the spring and summer months when the air is always fresh and cool.
Between the Nafud and the southern desert.
Khaibar harra, runs north-eastward across the whole width of Nejd, till it is lost in the sands of the eastern Nafud, north of Aneza.
In width extends almost continuously from the great Nafud to the Dahna.
The autumn rains fell that year abundantly in the Nafud towards Jauf, but very little in the basin of the W.
Snow falls on the Harra and on the Tehama range in northern Arabia, and Nolde records a fall of snow which lay on the Nafud on the 1st of February 1893.
The larger antelopes, so common on the African side of the Gulf of Aden, are not found, except one variety, the Oryx beatrix (called by the Arabs, wild cow), which is an inhabitant of the Nafud between Tema and Hail; it is about the size of a donkey, white, and with long straight horns.
Of birds the ostrich is found in the Nafud and in the W.
In Nejd the number of horses is, comparatively speaking, very small; the want of water in the Nafud where alone forage is obtainable, and the absence of forage in the neighbourhood of the towns makes horse-breeding on a large scale impracticable there.
These are kept most of the year in the Nafud, five or ten days' march from Hail, where they find their own food on the desert herbage.
The Nafud sands, too, are tufted in many places with bushes or small trees, and after the winter rains they produce excellent pasture.
The principal trade routes are those leading from Damascus to Jauf and across the Nafud to Hail.