M. Beudant m the Natron Lakes of Hung ary. 265 
and Bihar ^ which are contiguolis with the former : and it is im- 
possible that the argillaceous matters which occur at the margin 
of the lakes near Debretzin, could be any thing else than salife- 
rous clay. I may remark with regard to this, that the greater 
number of saliferous clays which I have had an opportunity of 
seeing, contain, like the argillaceous masses of the margins of the 
natron lakes, a certain quantity of carbonate of lime, and that 
they are more or less sandy. These mixtures naturally assist 
the decomposition of tlie muriate of soda, the one, by directly 
furnishing the substance which might produce it, and the other, 
by rendering the mass more porous, and thus facilitating the 
efflorescence of the natron. If decomposition does not take place 
in mines, it is, without doubt, because the heat is not sufficient- 
ly great, nor the moisture copious enough ; and espedally be- 
cause the air cannot have a sufficient circulation. It is probable, 
that on exposing to the day the refuse of salt mines, they would 
also form carbonate of soda. However this may be, it is not the 
less remarkable, that on following these plains, where the muri- 
ate of soda is constantly found in the waters, we arrive, without 
discontinuity, at masses of salt, which are the object of consider^ 
. able works. 
Sulphate of Soda . — Admitting in this manner the prolonga- 
tion of the saliferous deposits in the plain, the formation of sul- 
phate of soda may be easily explained ; for it is known that the 
sahferous clays always contain, nests of gypsum or sulphate of 
lime of greater or less size. Now, it appears that the muriate of 
soda must be decomposed by the sulphate of lime, in the same 
manner as by the carbonate ; the result must be sulphate of 
soda, which effloresces also at the surface-of the ground. We 
know, from the experiments of Gren^ tliat this decomposition 
is particularly active in winter, so that it must take place parti- 
cularly in the waters {eau^ meres) which remain at the bottom 
of some lakes. It is probable that it was tp a decomposi- 
tion of this kind that the sulphate of soda was owing, which 
formed at Dieuze, in the schlot and residue of the coppers, 
thrown out in h^ps df considerable size ; at the foot of which, 
M. Gillet de Laumont observed, in the winter of 1790, a spring 
of water impregnated with sulphate of soda. But besides the 
sulphate of lime, it is possible that there exists in the waters 
