Webster on Calton Mill. 235 
thense mass of it occurs, of more than an hundred feet in length, 
and from twelve to twenty feet in depth, containing entire shells 
and fragments of clay slate; it is singular that the whole mass 
assumes a striking appearance of stratification. In some places 
it appears that attempts have been made to separate it, proba- 
bly for the purpose of building ; for several old houses in Gwy- 
thian are built of it.” “It is around the promontory of 
New Kaye that the most extensive formation of sandstone takes 
place. Here it may be seen in different stages of induration ; 
from a state in which it is too friable to be detached from the 
fock upon which it reposes, to a bardness so considerable, that it 
requires a very violent blow from a sledge to break it.” 
“But it is on the western side of the promontory of New Kaye, 
in Fistril Bay, that the geologist will be most struck with the 
formation ; for here no other rock is insight. The cliffs, which 
are high, and extend for several miles, are entirely composed 
of it." The beach is covered with disjointed fragments, 
Which have been detached from the cliff above, many of which 
Weigh two or three tons.” 
There are three modes by which Dr. Paris conceives the 
lapidification of calcareous sand may be effected. Ist. “ By the 
Percolation of water through a hill of calcareous sand, by which 
itbecomes impregnated with carbonate of lime.” 2d. “The 
Percolation of water through strata containing pyritical substan- 
%s, by which it becomes impregnated with sulphuric salts.” 
“The. percolation of water through decomposing slate, or 
any ferruginous strata, by which it becomes impregnated with 
iron, alumina, and other mineral matter.” 
