84 Geological Society of London. 
certain depth, is expanded by heat so as to elevate the superincum- 
bent mass, the resulting fissures in this mass may then become mat- 
ters of calculation. According to Mr. Hopkins, rectilinear lines of 
dislocation will give rise to a set of longitudinal parallel fissures, and 
simultaneously to others precisely at right angles to them ; whereas 
in conical elevations, the fissures will diverge from a centre. If the 
general axis of elevation be curvilinear, the longitudinal fissures pre- 
serving their parallelism with it will be also curvilinear, while the 
transverse fissures being perpendicular to the former at their poimts 
of intersection will no longer be parallel. 
To return from this digression, I must now recall your attention to 
other papers relating to the carboniferous deposits of England. The 
coal-measures of the northwestern coast of Cumberland have been 
examined by Prof. Sedgwick and Mr. Williamson Peile, who have 
described the Whitehaven and other fields in great detail, illustrating 
their account with a map and sections. The recorded observations 
in numerous sinkings and borings, both in relation to the succession 
of the strata and to the complicated faults which intersect them, 
would have been involved in hopeless confusion, if they had simply 
consisted of a statistical collection of facts attested by miners; but 
in this paper, Prof. Sedgwick, aided by Mr. Peile’s practical and 
scientific knowledge, has compared the different sections and gener- 
alized the phenomena, giving unity and consistency to the whole, 
throwing the strata into distinct groups, and referring the several 
faults to different movements, to which successive periods of time 
may be assigned. 
In connection with these recent contributions to the history of our 
carboniferous strata, Iam happy to mention the excellent volume 
lately published by Prof. Phillips, forming the second part of his 
Illustrations of the Geology of Yorkshire. It is almost entirely de- 
voted to a description of the carboniferous or mountain limestone of 
Yorkshire and the north of England, a subject already admirably 
treated in some papers read before this Society by Prof. Sedgwick, 
particularly in his account of the carboniferous chain from Penigent 
to Kirkby Stephen.* As these geologists had separately explored 
the same ground, it is satisfactory to perceive that the leading divis- 
ions which they have proposed for the classification of the mountain 
limestone and associated strata, agree in every essential point. Mr. 
* Trans. Geol, Soc. 2nd Series, vol. iv. part 1. p. 69.—1835. 
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