88 
THE GEOLOaiST. 
tain limestone, as we continue our researches higher up in the beds 
we find their remains becoming more scanty, until at the top they are 
exceedingly rare. One bed is rich in zoophytes, another in goniatites, 
whilst another is composed of the broken fragments of Sanguino- 
laria, and the whole of the beds contain numbers of Spirifer imbricatus, 
which connects them like a huge bracket from top to bottom. Some 
rare geologizing may be had along the lower beds ; almost every 
stroke of the hammer lays open something novel. 
The remarkable fissures which occur in the limestone of Derbyshire 
have afforded matter of speculation to the curious for centuries ; the 
most remarkable one is called the Winnats, and is about a mile dis- 
tant from Castleton. It gives rise to the most sublime scenery, for 
the fissure is caused by the splitting of a hill in twain, and the steep 
precipices on either hand for the distance of a mile and a half, resem- 
ble the ruins of old towers and buttresses, in some places clad with 
ivy, and tenanted by bats and owls. Another such fissure is at the 
back of the town, and has been already referred to. In some places 
the passage at the bottom of this is not above three yards in width, 
and is much of a character, in other respects, with the Winnats. 
Much speculation has arisen as to the origin of these rents ; they occur 
at nearly right angles to the line of strike, and have doubtless been 
formed in the first instance by the upheaval and desiccation of the 
I'ocks, thus : — 
Fig. 2. 
Subsequent to this they have been worn and channelled by at- 
mospheric and aqueous action. They have been attributed to plutonic 
agency, but it needs little geological knowledge to see that the above 
theory is the true one. Along the lower beds in the Cave Dale there 
is another good spot or two for the geologist. Here are found 
numbers of trilobites, some quite entire 5 groups of the entomostra- 
can C^fker^e, and that rare fossil the Cudas radialis. One bed seems 
quite a nest of Pleiirorliyncus armatus^ although they are very fra- 
gile and require great care to extract them with tlie cone entire. 
Plutonic action has not been absent in the neighbourhood, for at 
the top of this fissure are beds of greenstone, and an imperfectly 
columnar basalt, whilst the limestone around seems to be somewhat 
crystallized by the heat to which it has been subjected by the in- 
trusion. 
Old Mam Tor, the " Shivering Mountain," in geological position 
lies just above the limestone. The shales which compose it are 
speedily decomposed by atmospheric agency, and hence have given 
rise to the popular name which the mountain bears. The inclination 
of its beds is E.N.E., and the intensity of their dip about 40°. These 
