T. S. Ellis — Low- Water Channels in Rivers and Estuaries. 451 



"Want of space forbids comment on many other points of interest in 

 the paper and in the discussion upon it. 



In a wide estuary, where the swing from side to side of a single 

 channel is not possible, there will be appearances of a struggle between 

 the disposition of the river-stream to go in a median line and the 

 influence of tributary streams in keeping open channels on either side 

 which the river-stream may, wholly or partially, adopt. Certainly, 

 while these influences exist, the formation of a single, continuous 

 channel is impossible. What would happen in the case of the 

 Hooghly estuary if all streams coming in on the eastern side were 

 diverted into the channel behind Saugor Island is an interesting 

 speculation. My belief is that the channel on the western side to 

 which the Iliver Haldia gives its name would become the principal one. 



Estuary conditions are well seen in the wide, crescent-shaped expan- 

 sion of the Mersey above Liverpool. Here, in the low-water channels 

 one can see the influence of the tide, of the main stream, and of the 

 tributaries on either side. I can imagine all of these latter on the 

 northern shore, east and west of Hale Cliff, diverted and brought in 

 at Widnes and at Grarston, so giving an unbroken front of more than 

 8 miles. Then, with no need for a channel there, the main stream 

 would follow a great curve on the southern shore, adopting the 

 channel kept open by the Weaver and other streams, which would 

 accord with the line of the tide coming up to Eastham, directed there 

 by the quay walls of Liverpool and of Birkenhead. 



Fig. 3 shows the estuary of the Exe with the low -water channel 

 on the left side at Topsham, 4 miles below Exeter. There is no 

 apparent obstruction to prevent a straight course to the sea; the 

 channel is, however, directed towards the right side, but not in 

 a straight line ; the upper part is inclined somewhat eastward towards 

 a similar inclination, westward, of the channel continuous with the 

 River Clyst. The two elbows, pointed towards each other, suggest 

 a former union and a comparison with similar features to be seen in 

 rivers and brooks, as mentioned in the previous paper.^ The channel 

 of the Exe crosses to the right side, where it receives streams coming 

 in near the entrance to the canal. Being here, there is no apparent 

 reason why the channel should not be continued on the same side and 

 unite with Powderham Pool, lower down. It does go over towards the 

 left side and unites with the channel of the Clyst. Again, with no 

 apparent reason why the united channel should not go direct, it 

 crosses over to the right side and receives the Kenn. Again, with 

 a direct course freely open, it goes over and unites with the Lympstone 

 Lake, which comes from the left side. Finally, the channel in its 

 progress towards Exmouth again inclines to the right and receives 

 several streams coming from this side. The influence of the tide in 

 maintaining channels is overrated. Here, the bar thrown up by the 

 current in the sea, running from west to east, would close the estuary 

 if a channel were not kept open by the stream. 



The course which the low-water channel in the estuary would take 

 if it were decided by the direction of the tide is clearly indicated by 



1 Geol. Mag., March, 1908, p. 111. 



