Academy of useful Sciences at Erfurt. 275 
from the sea and rivers much more easily than it blows 
away the dust; that there would be dreadful inundations 
every minute; that the banks of rivers and shores of the sea 
would-be uninhabitable, and navigation impossible, 
As to chemical affinities, properly. so called, M. Ber- 
thollet seems to have made that subject his peculiar do- 
main, and has imposed new laws upon. these affinities, of 
which we have often had occasion to give an account. His 
first memoirs upon this subject have been announced in our 
reports of 4n 8 and An Q, and his great work Statigue Che- 
mique, wliere he has consigned all his theory, in that of 411. 
We know that his principal idea consists in not consider- 
ing affinity, as was formerly the case, to be an absolute 
power; nor combinations as always uniform in the propor- 
tions of their elements. 
He shows, on the contrary, that many circumstances, fo- 
reign to the chemical nature of the substances placed in con- 
tact,—such as their more or less cohesion, pressure, tempe- 
rature, and, above all, their relative quantity,—influence their 
combinations, both as to the species and as to the propor- 
tion of the elements which enter into it. 
There is indeed very seldom any entire separation ; but 
when we place three substances in contact, for instance, 
there is produced a mixture, the one- with the two others, 
according to the power of the affinities of the Jatter; and 
when four substances are put together, if there is a_preci- 
pitate formed, it must be referred to the indissolubility of 
the combination, and not to a calculation rigorously appre- 
ciable in the sums of the affinities taken two and two. 
We may easily conceive that such new views, applicable 
as they are to phenomena so complicated, will be suscep- 
tible for a long time of ulterior developments. 
[To be continued. } 
ACADEMY OF USEFUL SCIENCES AT ERFURT. 
In the sitting of the above academy of the 6th of January 
last, Dr. Thielow, dissector in the anatomical theatre, read 
a memoir upon the esophagus of a man accompanied with 
a crop like that of a bird. He found this anomalous con- 
$2 formation 
