40 
little hills, which successively contract the bay, and one 
day will shut it up entirely. These sands are actually 
shifting and contain no other substances which can unite 
them. Notwithstanding this peculiarity, a plant of a lily 
kind and several others are growing on them, of which 
I have preserved some specimens. 
The climate of Tangier is mild. My thermometer, 
placed with all necessary precaution to avoid the direct 
or reflex impression of the sun, and to show^he true 
temperature of the atmosphere, marked only 24 deg. 
6 min.* of Reaumur, as the greatest heat ^hich was 
felt on the 31st August at noon, one of the hotte^days 
I experienced there. Another thermometer exposed 
to the sun, so as to receive all its influence, was at 39 
deg. 5 min. f on the 22d August at 2 o'clock in the 
afternoon. 
The greatest height of the barometer was at 28 in 1' 
9" Paris measure, and the lowest 27* 9', which estab- 
lishes a variation of 0 4' 9''. 
The smallest atmospherical humidity that was re- 
marked, was 38° of the hygrometer of Saussure, on the 
15th of July. The air is here in general cloyed with hu- 
midity; it is made sensible not only by the indications 
of the hygrometer, but also by all metals which oxidate 
rapidly, in consequence of this superabundance of at- 
mospherical moisture. 
The difference of the seasons is well marked at Tan- 
gier; the summer was constantly serene. Towards the 
equinoxes the rains began, as well as the high winds, 
which continued as constantly. At this season the thun- 
der was very frequent, and one man was killed by the 
lightning. 
* 86° 6' Fahrenheit. 
tll9° Fahrenheit, 
