“_Mourzuk, September 17_, 1822.
“When I wrote you last, I was just on the eve of departure for the
Tuarick country, and in about a fortnight from this date, I hope we
shall be on our way to Bornou. We found our journey to Ghaat very
pleasant, and our reception very flattering. We were among a brave and
warlike race, exceedingly superstitious; yet they were sensible; and
though remarkably strict Mahometans, yet liberal in their ideas. The
geology and botany of the country are nearly the same as in Fezzan,
which I cannot enter upon at present. We made long excursions in the
Wady (valley) Ghrurbi, and Wady Shiati, which Captain Lyon incorrectly
joins. In our course we examined the Trona Lake, which is situated
among amazingly high sand hills, running for several hundreds of miles
to the westward, and lie between the Wadies Shiati and Ghrurbi. The
lake is in a small valley which runs nearly E.S.E. and W.N.W. The north
and south sides are bounded by hills of sand about 400 feet high. The
bottom of the lake is a fine sand, on which is found the _cegoul_,
(apparently a species of silex) and a downy grass. Near the place where
we entered the valley there is a cluster of date palm trees, and a
small lake from which impure Trona is obtained. On the western side is
the Trona lake, surrounded by date trees, and its banks covered, on
almost all sides, with the grass I have mentioned, and a tall juncus.
It is almost half a mile long, and nearly 200 yards wide, of very
inconsiderable depth at present (July) from the evaporation of the
water, and many places are now dry which are covered in the winter and
spring. The Trona is deposited in cakes at the bottom of the lake when
the water is sufficiently saturated. The cakes are of various degrees
of thickness, from a mere film to several inches. The thickest I could
find was not more than three quarters of an inch, but at the beginning
of the winter, when the water begins to increase, it is of the
thickness I have mentioned, and is then said to be ripe. The surface
next the bottom is not unequal from crystallization, but rough to the
feel on account of numerous asperities. The upper surface is generally
found studded with small beautiful cubical crystals of muriate of soda;
the line of junction is always distinct, and one crystal is easily
separated from another; when not covered with the muriate of soda,
this upper surface is composed of a congeries of small tabular pieces,
joined in every position. When the mass is broken, there is a fine
display of circular crystals often radiated. The surface of the water
is covered in many places with large thin sheets of _carbo-muriate
of soda_, giving the whole the appearance of a lake partially frozen
over; film after film forms till the whole is a considerable thickness.
The soil of the lake is a dark barren sand approaching to black, of
a viscid consistence and strong smell; and on the recently uncovered
surface, near the banks, a black substance like mineral tar is seen
oozing out. The water begins to increase in the winter, and in the
spring it is at the _maximum_. The Trona is best about the commencement
of winter, but disappears entirely in the spring.
“The lake has diminished in size within the last few years, and if
care be not taken, the diminution will soon be much greater. Plants
are making considerable encroachments, and very shallow banks are
observable in many places. On inquiry, we found the quantity of Trona
had not sensibly diminished during the last ten years; but, perhaps,
this may be owing to there being always easily found a sufficient
quantity of it to supply every demand. The quantity annually exported
amounts to between 400 or 500 camel-loads, each being 4 cwt.—a large
quantity when the size of the lake is considered. It is removed only
when there is a demand. Then a man wades into the lake, breaks off the
Trona in large sheets, which he easily does, and hands it to others
outside, who are ready to remove all foreign matters, and to pack it in
the retecious substance found on the leaves of the date tree. The water
of the valley is good, and if a well be dug in the very border of the
lake the water is also good, and nearly free from saline impregnation.
There are a great many springs in Wady Shiati, and a number in the
wadies about Ghaat. All of them, however, were so exposed, that it
was impossible to make any correct observations. The maximum heat of
Mourzuk is 105 Fah.—a great difference from that mentioned by Captain
Lyon. The greatest diurnal change is about 15 degrees—a variation
which is pretty regular. The hygrometer of Kater varies from 360 to
410—an amazing small range. My worthy friend Clapperton, sends his
kind respects to you, and promises to write you from Bornou. We enjoy
the best health, and accomplished our summer’s excursion without
fatigue. Remember me kindly to Mr. P. Niell, and tell him the Flora
of Fezzan, and of the Tuarick country is very poor; but that in a few
months I expect to be on a soil more congenial to the votaries of the
fascinating goddess.”