43 
from some parts, or inundated others. But the reason is, that the same 
land is sometimes raised up and sometimes depressed, and the sea also 
is simultaneously raised up or depressed, so that it either overflows or 
returns to its own place again. We must therefore ascribe the cause to 
the ground, either to that ground which is under the sea, or to that which 
becomes flooded by it, but rather to that which lies beneath the sea, for 
this is more moveable." 
The pebble and sand-drifts of the Avon Valley east ©f Bristol, and other 
places, indicate that the present small river was once a tidal one for 
many miles beyond what is now the City of Bath. 
VII. 
On the Igneous Bocks ov Shropshire. 
By W. W. Stoddart, F.G.S., F.C.S. 
Head be/ore the Geological Section, March 9th, 1870. 
Abstract. 
After a brief review of the physical character of volcanic rocks, and 
especially the kinds found in the county of Shropshire, the author chose 
as a typical example the Wrekin near the market town of Wellington. 
The hill is the great centre of volcanic action in the vicinity of the Coal- 
brookdale Coalfield. In the latter the faults are very numerous and 
extensive, and it is a singular circumstance that the direction of the faults 
and of the eruptions of trap are nearly identical. 
We have in the Wrekin, if not the highest, one of the most interesting 
examples of a crystalline eruptive rock in England. Picturesque, grand, 
and abrupt in outline, it rises in the midst of a great plain. Its bold and 
barren summits have an elevation of fourteen hundred feet above the sea 
level, and often in particular states of the atmosphere, are hidden by the 
clouds. The sides are partially covered with fir trees, and the base with 
snowdrops at the proper season of the year, and which grow here in the 
greatest luxuriance. The view from the top is extremely fine, comprising 
the Shropshire coal and iron districts on the east, and Caradoc, Longmynd 
and Hope Bowdler Hills on the West. The summit and centre consist of 
red compact felspar, and at the northern extremity are quarries 
of characteristic Syenite, varying in colour from pink to purple. The 
strata through which this hill has been protruded are upper Lland- 
overy, containing the proper fossils. On the eastern side is a very good 
