J. J. Harris Teall—Effect of Earth-Movements. 303 
unconformably on the denuded edges of the old metamorphic rocks, 
and consist at the base of a conglomerate containing pebbles of the 
older Cambrian formation. If then, as is extremely probable, the 
N.W. and §.E. strike of the Cambrian rocks of all localities was 
produced by one series of earth movements, due probably to lateral 
pressure acting from the N.W. and §8.E., then this observation at 
Killery Harbour serves to fix the date of these earth movements in 
every locality. 
During the time which elapsed between the commencement of the 
Silurian and the close of the Carboniferous, the British Islands do 
not seem to have been subjected to any forces giving rise to anti- 
clinal and synclinal folds on a large scale. Various earth movements 
must have taken place, but these seem to have been gradual move- 
ments of elevation and depression, rather than movements due to 
lateral pressure. During the deposition of the Silurian, Old Red 
Sandstone, Devonian and Carboniferous rocks, depression must have 
taken place. The depression, however, was not a continuous one, 
for in Scotland there are at least two distinct unconformabilities, 
one between the Middle and Lower Old Red Sandstone, the other 
between the Upper and Middle. In Herefordshire and Shropshire, 
and the adjoining counties, no unconformability has been detected 
in the Old Red Sandstone, though one is strongly suspected. In 
Treland there is a marked unconformability between the Old Red 
Sandstone and Dingle beds, and in all probability another of less 
importance between these latter and the Silurian. In addition to 
the movements of elevation indicated by the unconformability, there 
must have been others, the only evidence for which is to be found 
in the change of character in successive deposits. Thus the Old 
Red Sandstone rocks, which succeed the Silurian conformably, were 
formed, in all probability, in a land-locked area, while the latter 
were certainly laid down in the open ocean. In order that a given 
spot may at one time be situated in the open ocean, and at another 
in a land-locked basin, it is necessary that elevation of some sort 
should take place in the adjoining area. 
The movements of this period were not, however, of such a 
character as to influence in any marked way the physical structure 
of the country, and therefore, although they have an importance of 
their own, which it is impossible to overestimate, we may leave them 
without further notice. 
The next great series of earth movements of the character we 
are more especially considering took place at the close of the 
Carboniferous period; like the previous earth movements of a 
similar character, they seem to have exerted an influence over the 
whole of the area occupied by Carboniferous formations. They 
may, however, be best studied in the district of Lancashire, Derby- 
shire, and Yorkshire, where facts may be observed which enable 
us to determine their geological ages. In the Q.J.G.S. vol. xxiv. 
p. 323, there is an able paper by Prof. Hull on the relative ages 
of the leading physical features and lines of elevation of the 
Carboniferous district of Lancashire and Yorkshire. In this paper 
DECADE Il.—VOL, YII.—NO. YIII. 23 
