262 PROCEEDINGS COTTESWOLD CLUB 1909 
and the Pill-house rocks. Below this, a tributary falls in, 
and, on the opposite side, is the opening of Oldbury Pill. 
Between them is a shoal in mid-stream. This illustrates 
an important principle. The shoal is between two 
channels, both necessarily kept open by the respective 
tributaries. Here, too, at the lower part of the shoal, is 
an instance of a tongue of the early tide, showing the 
direction which the tide would take if it were the dominant 
influence in deciding the line of the main channel. In 
this the stream is, really, the dominant influence. This 
tongue, “ The Whorl’s End” is, practically, always the 
same. If the line of it be produced upwards, past the 
Pill-house rocks, a similar feature will be seen in the 
shoal above. 
Below the mouth of the Wye is another illustration 
of the principle that a shoal in mid-stream indicates a 
need for a channel on both sides, probably due to tribu- 
taries. A strong confidence in this principle led me to 
predict, in discussing Mr Vernon Harcourt’s paper on 
“The River Hooghly,” that tributaries would, on a good 
map, be found opposite the James and Mary shoal, 
although not shown by the illustrations to the paper. 
This is recorded in the “ Proceedings of the Institute of 
Civil Engineers,” and I have given a copy of the Admiralty 
Chart with a paper in the “ Geological Magazine.”* 
A little lower the main channel is directed through 
The Shoots, a channel cut in the rock obliquely across 
the main line of the river, towards the mouth of the 
Avon. This forms a river curve just as really so as 
when, in an alluvial plan, the river swings from one side 
to the other to fall into and adopt a channel kept open by 
a tributary. Here the Severn crosses from its junction 
with the Wye to form one with the Avon. The line of 
1 Vol. clx. 1904-5, part 2. 
2 October, 1908. 
