258 DESERT OF BILMA. 



or island of natron. In one lake the island is 15 feet high, 

 and 100 feet in circumference. The natron is associated with 

 muriate of soda, or common salt. On the 12th they reached 

 Bilma, after passing through a wadey the greater part of the 

 way, which exhibited many patches of saline incrustations, 

 also beds of red sandstone, containing numerous nodules of 

 iron ore. The sandstone, hills exhibit, on their summits, 

 forms resembling ruins of towns and castles. Near to 

 Bilma are several salt lakes that afford very pure and well- 

 crystallized salt.* About a mile from Bilma is a spring of 

 beautiful clear water, which rises to the surface of the earth, 

 and waters a space of two or three hundred yards in cir- 

 cumference, which is covered with fresh grass ; but, pass- 

 ing this, the traveller must bid adieu to every appearunca 

 of vegetable production, and enter on a desert. From Bil- 

 ma, which was left on 16th January, the route led over loose 

 hills of fine sand, in which the camels sunk nearly knee- 

 deep. In passing the desert wilds, where hills disappear in 

 a single night by the drifting of the sand, and where all 

 traces of the passage, even of a large kafda, sometimes va- 

 nish in a few hours, the Tibboos have certain points in the 

 dark sandstone ridges which from time to time raise their 

 heads in the midst of this ocean of sand, and form the only 

 variety, and by them they steer their course. They halted 

 in the evening at Kaflorum, which is a nest of hills of coarse 

 dark sandstone. On the 17th bivouacked under a head 

 called Zow (difficult), to the east of which were found se- 

 veral wells. " This day, the 18th," says Denham, " the 

 sand hills were less high, but the animals sunk so deep that 

 it was a tedious day for all. Four camels of Boo Khal- 

 loom's gave in ; two were killed by the Arabs, and two 

 were left to the chance of coming up before morning. Tre- 

 mendously dreary are these marches ; as far as the eye can 

 reach, billows of sand bound the prospect. On seeing the 

 solitary foot-passenger of the kafila, with his water-flask in 



* Captain Lyon says,—" I found no one who knew of the salt lakea 

 of Poinboo laid down in all the maps ; but there is abundance of salt fit 

 Agrain (which is four days' journey trom Bilma, W.S.W.), and a large 

 lake, on the borders of whi(.h this article is collected. The Tuaricksgo 

 there and carry away great quantities to Soudan. This agrees with the 

 accounts of Domboo ; and, from the circumstance of Tuaricks going to 

 Agram, and the position of that place, I am led to imagine it may be the 

 eame Domt)oo, though under a diflbrent appellation." 



