366 Proceedings of the British Association. 
elder sister science Astronomy, and from the beginning now made, 
it was impossible to predict how far investigations like Mr. Hopkins’ 
might eventually be carried. ‘The observations of Mr. Hopkins held 
true in Cumberland, Derbyshire, and Flintshire ; and some of his 
cases of complicated dislocation were admirably illustrated in Caer- 
narvon and Stainmoor. Mr. Sedgwick had himself paid particular 
attention to the joints of rocks, and had found them connected both 
with their strike and dip. He had also observed some singular phe- 
nomena in the Westmoreland slates ; he bad seen in them two sorts 
of joints, and a cleavage which was in a different direction from the 
jointing. In South Wales the planes of splitting were in one direc- 
tion with very 
isfaction at the result of Mr. Hopkins’ paper, and expressed a hope 
that the phenomena of geology might, to a certain extent, be ex- 
plained by such simple laws as regulate the other branches of physi- 
cal science. With regard to the structure of rocks, which promised 
to throw so much light upon the subject, he proposed a new term 
for it, the symmetrical structure. In the examination of rocks un- 
_ der the three classes of calcareous, arenaceous, and argillaceous, he 
had remarked, that the regularity of the structure increased with the 
antiquity of the rock, which was well exemplified in the older slates 
and limestones. For this there must be a cause, and this must be 
a central heat, which has acted most upon the older formations, and 
least upon the new. Illustrations of the effects of heat upon strata 
may be obtained from those in contact with dykes, which produce 
symmetrical structure in rocks or clays through which they pass- 
Internal heat must then have caused the regular structure so gene- 
rally observed in rocks. The direction of the fissures pointed out 
by Mr. Hopkins in Derbyshire, corresponded with the observations 
of M. De la Beche in Cornwall, and of Mr. Conybeare in Glamor- 
ganshire. The phenomena of the direction of the joints were well 
worth investigation, as there was much uncertainty involved. They 
evidently pointed out the weaker points, or places of least resistance, 
where the disturbing force would operate with most effect ; and they 
may have been the result of consolidation, as we find them in con- 
glomerates, as well as in homogeneous rocks ; still it might be a 
question, if they were formed before or after dislocation. 
Section D.—Zootoey anp Borany 
Col. Sykes made a communication to the Seesion “On the oa 
tivated and. Wild Fruits of the Deccan.” 
