T. S. Ellis — Loio- Water Channels in Rivers and Estuaries. 453 



Powderham Pool, a tongue of the early tide and a permanent feature as 

 indicated by the fact that it has a name. Twice a day the tide 

 attempts to force a passage directly up the river, but succeeds only in 

 removing the mud left at high-water by the previous tide. Not only 

 is the tide unable to cut a way through the shoal; it has been power- 

 less to prevent the formation of it. Permanent features in estuaries 

 are much more interesting than changes ; they serve to indicate 

 conditions which conduce to stability. On examination of the map, 

 one of these tongues is seen opposite the mouth of the Kenn, where 

 the early tide has been deflected by a breakwater. Other tongues are 

 seen farther up the low-water channel, the course of which, evidently, 

 is decided by the stream. 



While, in the Exe, the low-water channel passes, through mud, 

 obliquely across the river from the mouth of one tributary to that of 

 another, in the Severn we can see the same thing where the channel 

 is cut in hard rock. The Wye, and a smaller stream just below, 

 are on the right side of the Severn, and the channel is on this side ; 

 then it passes obliquely across to the mouth of the Avon, along The 

 Shoots, a cutting in hai'd rock. We have evidence that it was really 

 cut by material moved by water; when the foundations for the 

 Portskewet Pier (for the ferry) were excavated, the holes were filled 

 at each tide, "sand, gravel, and stones double the size of a man's fist 

 being often found." The line of the early as of the higher tide 

 would not be along this channel if free to take its own course. 

 A tongue of the early tide, the Whorl's End, just above, a precisely 

 similar feature to Powderham Pool, has its point directed up the line 

 of the Severn, and is of the same shape as every map has shown it to 

 be for the last hundred years. The tide has, of course, been an active 

 agent in cutting The Shoots ; the line of this channel was decided by 

 the stream. 



The tide may serve to keep open or to close a channel, to prevent or 

 to cause the formation of new land, according to the presence or the 

 absence of a stream. Throughout a long line from Crossens, on the 

 Kibble, by Southport, no stream falls into the sea, and there is a great 

 accretion of land until, at the mouth of the Alt, the line of the 

 new land recedes. I have often thought that the Nene and all the 

 smaller streams between the Ouse and the Welland might be diverted, 

 right and left, into these rivers so as to give an unbroken front of 

 eight miles. Then a very large area of new land would quickly form 

 in the Wash between the two rivers as they extended their course 

 towards the sea along the coast of Norfolk and of Lincolnshire. 



To control the course of a river at high tide or at time of land- water 

 flood may be difficult, but the low-water channel, which, after all, 

 means the deep-water line, would, generally speaking, be easy. If 

 tributary streams fall in on one side only of the river, the channel will 

 be on this side only. A change may be made from one side to the 

 other if, at the point of crossing, no tributary come in on either. 

 So, too, in the case of either a river or an estuary of moderate width, 

 a channel may be fixed in mid-stream if the tributaries, singly or 

 ■united, be carried out by training-walls to fixed points on either side 

 of the intended channel, not necessarily a straight one if it afford 



