262 M. Beudant m the Natron Lakes of Hmigary, 
so, that the greater number of the lakes are dried up at mid- 
summer, and that the natron which effloresces at the surface 
is then collected. The efflorescence is renewed at the end of 
three or four days, and it may then be collected anew ; so that 
a great quantity may be collected in the course of a summer. 
But there are deeper parts where the water never dries up, but 
contains a great quantity of carbonate of soda (50 or 60 in the 
100, according to Ruckert), which crystallises during the cold 
nights of autumn. This saturated water is conducted to the 
manufactories, and reserved for the labour of winter. 
Examination qf the Natron collected . — Not having an oppor- 
tunity of seeing the efflorescences on the ground where they are 
formed, I examined the natron which had been previously col- 
lected. It was mixed with a pretty considerable quantity of 
grey argillaceous matter, and contained much muriate of soda, 
as well as a certain quantity of sulphate. I had afterwards an 
opportunity of seeing it with the peasants in the Grande Cu- 
manie^ where it was also gathered in the marshes which border 
the Theiss, and it contained the same salts also, although in less 
quantity. I made the same observation on the natron gathered 
in the plains of the Lake of Neusiedel. It therefore appears 
evident, that the carbonate of soda is never pure, and that in 
Hungary, as in all the other places where it is found, it is al- 
ways mixed with muriate of soda, in greater or less quantity. 
Origin of the iVa^row.— Such are the facts which I have been 
able to collect in the midst of those desert plains, where the geo- 
logist, being able to examine only the uppermost pellicle of the 
globe, finds himself suddenly arrested in the progress of in- 
quiries which might prove of the greatest interest. The prima- 
ry object which presented itself here, was to determine the ori- 
gin of this immense quantity of natron which is daily efflorescing 
at the surface of the earth, and which is found every where in 
the waters which cover the plains of Hungary. But the data 
which we possess cannot permit us to say any thing with cer- 
tainty on this subject, and we are limited to more or less pro- 
bable conjectures, which, however, deserve a certain degree of 
attention, because they are deduced from facts, and rest upon 
no hypothesis. Ruckert was of opinion that the sub-carbonate 
of soda occurred already formed in the sand or clay, at a cer- 
