177 
the following observations of Sir Charles Lyell* as to cal- 
careous springs : — 
“ Many springs hold so much carbonic acid in solution that 
they are enabled to dissolve a much larger quantity of calcareous 
matter than rain-water ” 
“ Calcareous springs, although most abundant in limestone 
districts, are by no means confined to them, but flow out indis- 
criminately from all roclc formations. In central France, a 
district where the primary rocks are usually destitute of lime- 
stone, springs copiously charged with carbonate of lime rise up 
through the granite and the gneiss. One of these springs at 
the northern base of the hill on which Clermont is built issues 
from volcanic peperino, which rests on granite. It has formed 
by its incrustations an elevated mound of travertin , or white 
concretionary limestone, 240 feet in length, and at its termina- 
tion 1 6 feet high and 12 wide . 55 
I presume that this is the same spring which forms incrus- 
tations on birds 5 nests or similar natural objects, in a very short 
time, as I was told when there. 
“ The more loose and porous rock (like the upper floor) is 
called tufa, the more compact (like the lower floor) travertin.” 
“ If we pass from the volcanic district of France to that 
which skirts the Apennines, in the Italian peninsula we meet 
with innumerable springs, which have precipitated so much cal- 
careous matter that the whole ground in some parts of Tuscany 
is coated over with tufa and travertin, and sounds hollow 
beneath the foot. 55 
“ The water which supplies the baths of San Fillipo falls 
into a pond where it has been known to deposit a solid mass 
thirty feet thick in about twenty years. Near the hot baths 
called the Bulicame, a monticule is seen about 20 feet high 
and 500 yards in cfrcumference, entirely composed of con- 
cretionary travertin. The laminae are very thin, and their 
minute undulations so arranged that the ivhole mass has at once 
a concentric and radiated structure .” f 
The rest of Sir C. Lyell’s observations may be read with 
advantage, but are too long for me to quote. 
In reference to the probable flow of water through the 
cavern, I would adduce the following observations of Louis 
Figuier in his Primitive Man, which seem to me well-founded 
and applicable to Kent’s Cavern as well as that of Brixham. 
“ It is supposed that the bones in question were deposited 
in these hollows by the rushing in of the currents of diluvial 
water which had drifted them along in their course. A fact 
* Principles of Geology, 7th ed. 1847, pp. 238 to 244. + See p. 12. 
