428 Proceedings of 
mofphere. This diminution in the Defert is produced by 
the increafe of heat arifing from that communicated by the 
rays of the fun to the fand with which this ftratumis in im-* 
mediate contact. At fea it takes place when, by particular 
circumftances, fuch as the action of the wind, the lower 
ftratum of the atmofphere holds in folution a greater quan= 
tity of water than the other ftrata. In this ftate of things: 
the rays of light, which come from the lower parts of the. 
heavens, having arrived at the furface that feparates the lefs. 
denfe fvatum frem thofe above it, do not pafs through that. 
ftratum, but are reflected, and paint in the eye of the eb- 
ferver an image of the heavens, which appearing to him to 
be below the horizon, he takes it for water, when the pheno- 
menon oceurs at land. If he is at fea, he thinks he fees in 
the heavens all the objects which float on that part of the: 
furface occupied by the image of the heavens, 
Third Sitting, Frudlidor 16. 
. €. Berthollet read a memoir on the formation of ammd- 
nia under feveral cireumftances where the exiftence of # 
has not hitherto beer fuppofed. 
- €. Sulkowfky read a defeription of the route from Cairo 
to Salehié. The route which the French army followed in 
purfuing Ibrahim Bey had been before unknown. Thofe. 
whe proceed from Cairo by the gate of Nafr firft enter the 
Defert where there are a great many houfes now deferted. 
The village of Elmalarié, which is found on this route, was 
the ancient Heliopolis. In another village called Elmare- 
there are thoufands of palm trees. To the right of this route 
there is nothing except fandy deferts; but on the left there 
is abundance of cultivated land. The places-through which 
the army pafled were Lacoubey, Elhanea, Elmenic, Belbeys,. 
Souva, Coraim, Salehié, and a great many others, which it 
only traverfed in. the courfe of a rapid march. 
C. Berthollet communicated the refult of his examination 
of the gun-powder foundin the cafile. of Cairo, This pow- 
dex 
