518 | REPORT—1890. 
V-shaped estuaries has been suggested other than that of comparing the 
contoured plans and the longitudinal section taken down the highest 
banks and lowest channels, together with the cross sections which have 
been plotted on the plans. These are very similar for the similar tanks 
and corresponding periods. They show that the slope in the channels 
down to low water is nearly the same as in the rectangular tanks, the 
level of low water being reached at distances from the head of the estuary 
a little greater than in the rectangular tank, and a little greater in the 
long V than in the short. Below low water the slope in the channels is 
less than in the rectangular estuaries, which is, doubtless, a consequence 
of lateral spreading. The slope of the banks is much less than in the 
rectangular tanks, and these extend from two to three times as far from 
the top of the estuary according to the angle of the V. 
The range of observations on V-shaped estuaries has necessarily been 
limited, and time has not sufficed to duly consider all the results obtained, 
but the following conclusions may be drawn :— 
(1) In similar shaped V-estuaries configurations similar according to 
the simple hydrokinetic law are obtained irrespective of scale, provided 
the criterion of similarity has a value greater than its critical value. 
(2) That the general character is that of a main channel and high banks. 
(3) That the estuaries are longer in a degree depending on the fineness 
of the V than rectangular estuaries with corresponding tides, while the 
low-water contour reaches to nearly the same distance from the top of 
the estuary. 
ll. In the experiments with a long (fifty miles) tidal river increasing 
in width downwards slowly until it discharges into the top of the V-shaped 
estuary the character of the estuary is entirely changed. The time 
occupied by the tide getting up the river and returning causes this 
water to run down the estuary while the tide is low, and necessitates a 
certain depth of water at low water, which causes the channel to be much 
deeper at the head of the estuary. In its effect on the lower estuary the 
experiments with the tidal river are decisive, but as regards the action 
of silting up the river further investigation is required, both to establish 
the similarity in the models and to ascertain the ultimate state of 
equilibrium. 
It may, however, be noticed that the general conditions of the experi- 
ments in Tank E do not differ greatly from the conditions of some actual 
estuary, as, for instance, the Seine. This estuary is some thirty miles long 
before it contracts to a tidal river which extended fifty miles further up. 
In the model the tidal river reduced to a 30-foot tide is forty-nine miles 
long and the V extends down twenty-eight miles further, while the results 
in the model show about the same depth of water in the channel down 
the estuary as existed in the Seine before the training walls were put in. 
12. The Effects of Land Water.—These come out clearly in the experi- 
ments, which show that the stream of land water running down the 
sand, although always carrying sand down, does not tend to deepen its 
channel, since at every point it brings as much sand as it carries away. 
If it comes into the estuary pure, it carries sand from the point of its 
introduction and deposits it when it gets to deep water, somewhat 
deepening the estuary at the top and raising it below, which effect 
is limited by the influence the diminished slope has to cause the flood 
to bring up more sand than the ebb carries down. The principal effect 
of the land water is that running in narrow channels at low water, which 
