882 Letter from Dr Oiidney to Professor Jameson , 
ges of the process are very distinct ; first a thin crust, like hoar- 
frost, that gives the crackling sound of soft ground lately fro- 
zen over ; it increases gradually in thickness, till it arrives at that 
of many inches, sometimes even a foot. 
At present I will not enter into any explanation, but shortly 
I will be able, I hope, to enter on this subject, and others on 
the geological structure of Fezzan. The courier is now wait- 
ing, and camels, that are to convey me to Ghraat. My worthy 
friend Clapperton and I are just setting out there, that we may 
render our delay here as serviceable as possible. The Marick 
country is perhaps interesting only on account of its inhabi- 
tants, who appear a brave and independent race. He and I 
have been at Zuela, and both could not but be struck with the 
general uniformity of scenery and structure. He desires to be 
kindly remembered to you, and will write you very soon. We 
expect to be able to set out for Bornou in two or three months. 
Excuse this hasty letter ; and believe me, &c. 
Dr Oudney to Professor Jameson. 
My Dear Sir, Murzouk , \$th Sept. 1822. 
When I wrote you last, we were just departing for the 
Zwenich country ; I hope in about a fortnight after this we 
will be on our way to Bornou. We found our journey to 
Ghraat very pleasant, and our reception was very flattering. 
We were among a brave warlike race, exceedingly superstitious, 
yet sensible ; uncommonly strict Mahommedans, yet liberal in 
their ideas. The geology and botany of the country nearly the 
same as Fezzan, which I am not able to enter into at present. 
We made long excursions in Waday Ghrurbi and Wadies 
Shiati, which Captain Lyons incorrectly joins ; in our cruize 
we examined the Trona Lake. It is situated in the midst of 
amazingly high sand-hills, that run for several hundred miles to 
the westward, and lie between Wadies Shiati and Ghrurbi. It 
is in a small valley which runs nearly ESE. and WNW. The 
north and south sides are bounded by hills of sand about 400 
feet high. The bottom is a fine sand, on which are found the 
Agoul (apparently a species of Ulex), and a downy grass. 
3 
