592 Dr. DavnzxY on a certain Kind of 
formerly examined the mucous matter deposited by the waters 
of Valdieri in Piedmont,—a thermal spring containing sulphu- 
retted hydrogen,—and that he fully satisfied himself, as to the 
whole being derived from bodies that once possessed organiza- 
tion, having traced the different stages of decomposition and 
change exhibited by the several parts of the same deposit, from 
a structure completely analogous to that of a Conferva, to a 
gelatinous mass in which no distinction of parts was visible. 
It has been remarked, indeed, by Anglada, Gimbernat, and 
others who have noticed this phenomenon, that a portion of the 
substance in question is chemically dissolved in these waters ; 
and although I cannot admit the proposition as a general truth, 
yet I have myself found, that the thermal waters of Aix in Savoy; 
and those of Chaudes-aigues in the department of Cantal in 
France, even when carefully filtered and: completely :transpa- 
rent, begin to exhibit traces of a substance. of this kind as soon 
as they are concentrated. 1*6 
But this only proves, that the mucous matter dixived from 
such sources is soluble in water *, and that the growth of these 
bodies takes place, not only in the reservoirs which receive the 
water after it has escaped from the earth, but also:in the sub- 
. terranean canals through which it finds its way in reaching the 
surface ;—a notion which will be admitted without difficulty, 
when we reflect upon the luxuriant growth of many species 
belonging to the lower tribes of animals and vegetables in spots 
equally secluded from light and the external air. Neither, if 
the substance called zoogene by Gimbernat agree in its charac- 
ters with this product of the Pyrenean waters, (and I amin- 
duced to suspect that it does, from his enumerating Aix in 
Savoy as one of the spots in which he found it,) need: we 
* During the process of evaporation it seems to undergo some chemical We; 
for 1 it is no longer soluble in water, when once separated from it. 
be 
