DESCRIPTIONS OF EGYPT. 
131 
stances with which the water of the lakes is im- 
pregnated are the muriate, the carbonate, and the 
sulphate of soda. The last substance is only found 
in small quantities, but the others predominate in 
their turns, according to the nature of the springs, 
and the quality of the adjacent soil. In this im- 
mense natural laboratory of soda, the original sub- 
stance from which the natron is formed, according 
to Berthollet, is common sea salt. According to 
the Arabs, the soil impregnated with natron ex* 
tends to the distance of twenty days' journey into 
the desert. The season of collecting this substance 
is in the month of August, in the interval between 
seed-time and harvest. The natron trade was for- 
merly engrossed by the inhabitants of the canton 
of Terane, who annually collected about twenty- 
five thousand quintals, the greater part of which 
was exported to Venice, France, and England. 
The use of natron ascends to a very high anti- 
quity. Pliny, who prefers the Macedonian to the 
Egyptian, on account of its superior purity and 
clearness of colour, celebrates its numerous medi- 
cal virtues, and relates, that, when liquified with 
sulphur, it was formed into vases. Near one of 
the lakes, the vestiges of a manufactory of glass 
may still be traced, by the fragments of scoria, and 
the ruins of its furnaces. Perhaps a more favour- 
able situation could not have been selected for pro- 
curing the two materials of glass, soda, and vitri- 
fiable sand. 
