voi.. XIX. (i) THE CONTROl. OF RIVER CHANNELS 
45 
been left to shape its own line between b and c. It is shown 
as having taken the shortest possible course from a to d, having 
regard to the minimum of curve. If, however, it were diverted 
from the line c d to that of c e, then the shortest course would be 
in a line farther south, as shown. Supposing that, for any 
reason, the river had described a great curve extending as far 
northward as f , there would still be a good flowing line from a to d, 
but the line from a to e, though the river might follow it, would 
require two extra curves. If the river were tidal and the tide 
came up the line from d to c, the course would be favourable for 
going on to f. But if the line of the tide were from e to c, it 
would tend to continue in a more southern direction towards b. 
The Yorkshire Post of January i6th, 1911, contained a 
sketch map of the upper part of the Humber, with an account 
of some projected works which had been discussed at a meeting 
of the Conservators, as reported in the same paper on the 13th. 
1 became interested in the question what were the natural 
conditions of a river which was supposed to require an ex- 
penditure of £132,000 for its regulation ? The Humber is 
really an estuary common to the Ouse and to the Trent, which 
unite at Trent Falls. The part shown in Fig. 10 is divided 
into three sections.^ The first, which is directed north-east, 
is expanded in the middle and encloses a large shoal, the 
Whitton Sands. The second is directed south-west in a single 
channel. The third branches from the line of the second, 
and is directed to the east ; it encloses, with a continuation 
of the second section, an island, formerly a shoal — Read’s 
Island, Thus is described a roughly-shaped figure-of-eight, 
bent in the middle and enclosing in the two loops the two 
shoals. Taken as a whole, there is an elongated double curve 
very similar to those shown in Fig. 5, and having, like them, 
tributaries flowing in on the convexities. Each section 
illustrates the law that when a river’s bed is too wide for its 
requirements at low- water, a shoal will form. This may be 
on either bank, but if tributaries fall in on both sides in 
sufficient number or size to keep open a channel, the shoal will 
be in island form. Of the two alternative channels neither is 
I Ordnance Map, one inch scale, small sheet 8o, price is. 
