32 PROCEEDINGS COTTESWOLD CLUB 1915 
It does not continue in this direction, but turns downwards, 
and, in doing so, it describes a wide curve as it passes the end 
of the groyne. But, according to the well-known law of 
Newton, a body moving in a straight line would continue in 
that line unless compelled by some external force to change it. 
The force of gravity tends to keep the river in the downward 
line and so to prevent deviation further than the groyne 
compels ; and this influence is very much promoted by the 
traction of the stream lower down the line. In passing round 
the end of the groyne, a curve is necessary : a river cannot flow 
smoothly along a series of straight lines joining each other at 
an angle. In order to have a flowing line there must be a 
curve, the extent of which is stated, on authority, to vary in 
proportion to the width of the river. This is not quite cor- 
rect : a narrow stream may describe a broad curve, but a wide 
stream cannot describe a narrow one. Every river has its 
minimum of curve. Assuming this to be correctly shown as 
regards Fig. 2, the river is taking the shortest possible route 
round the end of the groyne. 
Fig. I. 
Fig. 2 . 
Fig. 3- 
