J. J. Harris Teall—Effect of Earth-Movements. dol 
and on them, as on a floor, the Cambrian rocks were formed. Dr. 
Hicks believes that a large continent, formed principally of these 
rocks, existed very much in the position now occupied by Europe, 
and that the Cambrian deposits were formed on the borders of this 
continent as it gradually became submerged. The submergence, he 
supposes, commenced in the West, where the Cambrian rocks are 
thickest, and gradually extended eastwards. If, however, we hold 
with Dr. Hicks that these Pre-Cambrian rocks were originally dis- 
tributed over the whole of the British Isles, and formed the floor on 
which the later deposits were formed, we must not suppose that at 
present they would be found at all points, if the later deposits were 
removed. Owing to the depression which accompanied the deposi- 
tion of many of the later deposits, such as the Cambrian, the early 
Pre-Cambrian floor must have been buried sufficiently deep in the 
earth’s crust to have been completely fused. 
We conclude, then, from*the arrangement of these early rocks, that 
the first earth movements of which we have direct evidence took 
place along axes running N.W. and 8.E., and that they were probably 
due to lateral pressure acting from N.E. and §.W. 
Passing over, for the present, the evidence of additional Pre- 
Cambrian earth movements furnished by the Pebidean rocks of 
Hicks, we come to the Cambrian rocks proper. And here it must 
be understood that I use the term Cambrian to include the entire 
series of deposits intervening between the Longmynd, Harlech and 
Llanberis group, and the Llandovery beds. Whatever may be our 
views as to the propriety of abolishing the term Lower Silurian 
from geological nomenclature, there cannot be a shadow of a doubt 
that for our present purpose the rocks indicated above must be 
treated as forming one great natural group. They have all been 
affected by the same earth movements. 
The total maximum thickness of the Cambrian series, according to 
Woodward, is about 380,000 ft. in Wales, and 20,000 ft. in the Lake 
District. In the Highlands of Scotland? it is quite impossible to form 
an estimate of the total thickness, on account of the difficulty of 
determining particular horizons. Now since the basement beds of 
the Cambrian consist of deposits that were certainly formed in shal- 
low water, if not in inland seas or lakes, we must suppose that during 
the Cambrian period there was depression at least to the extent of 
the thickness of the deposit, that is, to the extent of 30,000 ft. 
To this depth in the crust of the earth must the original surface, 
composed as we have seen of Dimetian and Pebidean formations, 
have been carried. 
The Cambrian rocks are now found to be arranged in anticlinal 
and synclinal folds, running N.E. and §.W., showing that at the 
close of the Cambrian period, and, as we shall see in a moment or 
two, before the Silurian period, they must have been puckered up 
by lateral pressure acting from the N.W. and 8.E. over the whole of 
our area. 
This anticlinal and synclinal arrangement of rocks is well seen on 
1 Are these rocks Cambrian or Pre-Cambrian ? 
