— 
n 
Organic Matter found in Sulphureous Springs. 597 
found at Vichy*, and in several other warm springs, that liberate 
carbonic acid, but are destitute of sulphuretted hydrogen*, and 
notwithstanding the similarity of external appearance belonging 
to the specimens of this substance which are taken from different 
localities, I am inclined to doubt whether they possess anything 
in common, except the earthy and ferruginous matter with which 
they are respectively charged. 
In support of this opinion, I might appeal to a drawing exe- 
cuted by M. Heuland, to whom I am also indebted for that of 
the Oscillatoria from Greoulx, which represents the appearances 
exhibited under the microscope by a portion of the red coria- 
ceous-looking substance, already alluded to as having been 
found at Bagneres de Bigorre. 
From this it would appear, that the medium, by which the 
earthy and ferruginous matters disengaged from the water were 
in that instance held together, consisted of nothing more than 
the parenchyma of decayed leaves, some of the stomata of which 
were still visible. 
Without meaning indeed to deny, that Conferve are met 
with in thermal waters of all descriptions, I am inclined to 
believe, that they are peculiarly abundant in sulphureous ones ; 
for it has never occurred to me to witness, in any of the nume- 
rous mineral springs I have visited in different parts of Europe, 
an accumulation of organic matter at all comparable to that, 
which takes place in some of the sulphureous ones of the Py- 
renees already alluded to; and, whereas there are many of the 
purer kinds of hot springs, such as that of Buxton, which do not 
appear to contain, or to deposit, any organic matter whatsoever, 
 Iscarcely know one containing sulphuretted hydrogen, that does 
not exhibit more or less of it. 
* Asthat of Campagne in Roussillon, on the road from Carcassone to Perpiguan. 
XXXIII. On 
