165 
Before quitting the Shibden valley, I must call the atten- 
tion of the meeting to a spring situated behind the Lee, on the 
same range of hill, about a mile to the north of the one just 
mentioned. It is remarkable as being so charged with calca- 
reous matter as to precipitate tufa or calc-sinter along its 
course, and completely whitewash the wall below, from which 
it falls in cascade. Destitute of limestone as a formation, in 
that neighbourhood, and very sparingly supplied, I believe, 
with the slaty marl already mentioned, whence comes this en- 
crusting lime ? Thermal springs, it is kno^Ti, afford it even 
from gneiss and granite under circumstances easily explained, 
but cold ones, so far as I know, in lime stone districts only. 
Is it a gypseous spring ? But it certainly contains the car- 
bonate of lime, as well as selenite. 
At Widdup, in Heptonstall, is a spring which deposits 
quantities of ochre, or peroxide of iron ; and at Gorpley 
Clough, beyond Todmorden, there is one so largely charged 
with lime as to precipitate vast quantities of calcareous tufa, 
and occasion some formative changes in its vicinities. Sta- 
lagmitic-like masses are here found abundantly, of which 
these, presented to me by Mr. Gibson, are samples. Not far 
distant from this last place are frequent throws-up of strata 
of the Mountain Limestone, and attempts are now making^ 
near Scaitcliffe, to work lead ores, galena having been found 
in interrupted beds and masses. To the solvent power of 
water, greatly charged with carbonic acid, percolating the 
various rents and fissures of their formation, these mounds 
of chalk must of course be ascribed, the excess of carbonic 
acid flying off on the spring quitting its subterranean labora- 
tory. It is to the presence and solvent power of fixed air, 
or carbonic acid contained in the filtering waters, that the 
internal decomposition of rocks, and the re-arrangement of 
the particles observable in the various fossil shells, must 
be referred : this acid, on seizing their lime, (for which it has 
