SCIENTIFIC NEWS. 
73 
and beauty, calcareous spar, chlorite, and, in some instances, 
adularia. The slate of Tintagel appears to bear a near resem- 
blance to that of Snowden, and, like it, occasionally presents 
the impressions of bivalve shells. 
The reading of Mr. Farey’s paper on the Ashover denuda- 
tion, was concluded, and thanks were voted for the same. 
This portion of Mr. Farey’s paper contains a detailed account 
of the several strata represented in the map and sections, be- 
ginning from the lowest of those that are known. 
The fundamental rock of Derbyshire is the fourth limestone. 
It is supposed to lie at the depth of about 350 yards below the 
level of the river Amber, in Ashover valley. It rises towards 
the surface under Matlock valley, and actually bassets in Griff- 
dale. The thickness of this bed is unknown ; but as the deep 
vale of the Dove is entirely excavated in it without discovering 
the bottom of the bed, its thickness cannot be less than 350 or 
400 yards. It is generally a pure calcareous free stone, of a 
whitish yellow colour, disposed regularly in very numerous 
strata. These consist either of very white marble, or of aggre- 
gations of small rhombic crystals. Towards the top it is very 
compact and porcellaneous. Few of the beds are without or- 
ganic remains— in some are found small anomia, in others en- 
trochi, or turbinated shells, cornua ammonis, nautili, and 
branching coralloids. This rock is superficially cracked, so as 
to present a columnar appearance — beneath it is much rent, 
and abounds in shakehole and large caverns with water swal- 
lows. Some of the fissures connected with the surface are 
filled with clay, sand, and quartz pebbles. The veins are 
filled principally with calcareous spar, heavy spar, and fluor 
spar. They also contain in their upper part galena, calamine, 
manganese, red iron ore, white China day, and stratin. 
Upon the fourth limestone lies the_third toadstone. The 
most eastern basset of this rock is at Bonsall upper Town. Its 
thickness in different parts is very various, from four feet to 80 
yards. Its usual appearance is that of a cavernous strong mass, 
of a dirty purplish brown hue-— often it is of a dark blue colour 
with shining specks as hard and sonorous as cast iron — also 
of a light green or bluish grey colour, and rarely it appears of 
a gritty yellowish stone called Davestone. Its structure, when 
recent, is amygdaloidal, the cavities being filled with green or 
whit# 
