550 REPOR?—1904. 
metapodial bones they are more like Procolophon. ‘Their generic relation is not 
determined. 
Two other animals of smaller size are indicated on the same slab. Both have 
the digits parallel, and apparently four in number, like some from the Trias of 
Cheshire. ; 
A cast of this slab was made by the late Professor v. Zittel. and given to the 
author for description and presentation to the British Museum. 
This is the first record of footprints in the Karroo rocks, 
11. Report on Life Zones in the British Carboniferous Rocks,—See 
Reports, p. 226, 
be 
MONDAY, AUGUST 2 
The following Papers were read :— 
1, Discussion on the Nature and Origin of Earth Movements. 
i, Introduction, By AuBRey STRAHAN, M.A., F.R.S. 
The subject proposed for discussion is the nature and origin of those move- 
ments of the earth’s crust which have manifested themselves in the fracturing, 
overthrusting, and folding of strata. These movements have been in operation 
from the earliest to the latest geological periods; and, though they have been 
intermittent so far as any one region is concerned, there is reason to believe that 
they have been more or less continuously in action throughout the world as a 
whole. Their operation, in fact, is essential to the existence of a land surface, 
for in their absence all rocks projecting above the sea would be worn away, and 
the globe would become enveloped in one continuous ocean. 
Notwithstanding these facts, and though they have been the object of pro- 
longed study, no theory as to the cause of the movements has commanded 
universal acceptance. Without attempting to enter in detail into the various 
theories which have been advanced, I will merely point out, for the purposes of 
the present discussion, that, while some hold that the shrinking of the globe by 
cooling and the efforts of the crust to adapt itself to the shrinking interior are the 
prime causes, others maintain that the scale on which folding and overthrusting 
in the crust have taken place is out of all proportion to the shrinking that can be 
attributed to such a cause. 
Earth movements may be divided into two principal classes—namely, move- 
ments of expansion, which are evidenced in normal faulting; and movements of 
compression, such as are indicated by the buckling, overthrusting, and shearing of 
strata, by the superinduced structures of cleavage and schistosity, and by the 
extrusion of granitic rocks and metamorphism. All these phenomena have been 
made the subject of special study, and I believe that no better opportunity could 
be found than a meeting of this Section for comparing the views of specialists 
upon them, and for ascertaining how far those views point to a general agreement 
as to the causes of the earth movements upon which these phenomena are 
attendant, 
ii, Contribution by Dr. Joun Horne, F.R.S. 
The Earth Movements in the North-West Highlands. 
The nature of the earth movements in the North-West Highlands in post- 
Cambrian time was illustrated by a series of horizontal sections across the belt of 
complication, that stretches from the north coast of Sutherland to Sleat, in Skye. 
