TRANSACTIONS OF SECTION G. 611 
He suggested that the question will naturally be asked : What is the remedy 
or partial remedy for this trapping of the travelling sand and corresponding 
erosion on the leeward side of a harbour? and explained that previously the 
only method of escaping from the impounded material seems to have been to 
periodically extend the arm of the harbour further seaward, as proposed for 
Madras. This meant a tremendous cost, and the results were often not satisfac- 
tory, for as the pier was advanced the shore also advanced. It had been sug- 
gested that instead of doing this openings should be left through the shore ends 
of the harbour arms for the sand to pass through; but this suggestion was not 
practicable, for immediately the travelling material passed through the opening 
the wave behind it did not possess sufficient force to move the material through, 
especially where the width of the harbour was considerable. 
The author suggested that in order to modify this trapping of the sand the 
ground plan of the harbour, instead of showing the piers to run out at right 
angles to the coast, or approximately so, should show that on the side facing the 
direction of the travelling material to project from the coast at an angle of 45°, 
the additional area thereby enclosed by the harbour piers could be utilised, 
among other purposes, for that of wharfage. The travelling material would, he 
stated, pass around the harbour projection if the plan of the harbour was on 
these lines, and would supply the coast on the lee side of the harbour with a 
natural protection of sand and shingle. 
He illustrated the various points referred to by numerous diagrams and 
photos, and stated that in arriving at his conclusions he carried out various 
experiments, which he described in the paper. He made the suggestion that 
where it can be proved that erosion has occurred, and is still taking place, owing 
to the projection of harbour piers, or the lengthening of such piers, or the con- 
struction of a spur breakwater from such piers, the harbour authorities should 
be called upon to contribute towards the cost of the protection of such a coast as 
far as the affected area is concerned. He also suggested that in the granting of 
powers by Parliament for the construction of new harbours, it should be made 
compulsory that contributions shall be made towards the cost of the prevention 
of erosion, where it can be proved later that protection works are necessary in 
consequence of such harbour projections. 
4. The Transport and Settlement of Sand in Water, and a Method of 
Exploring Sand Bars. By Dr. Jonn 8. Owens, A.M.Inst.C.E., 
GS. 
This paper, illustrated by experiments, dealt with certain phenomena accom- 
panying the movement of sand in water. Sand ripples were shown travelling 
under the influence of a current. The grains being swept by the current from 
the back of the ripple and deposited on its face, the ripple-form thus moved 
forward with the current by a process of erosion of its back and accretion of 
its face. This was demonstrated by means of a trough with semi-circular ends 
and a longitudinal partition in the middle, thus forming two channels. The 
water was made to circulate up one channel and down the other, and the move- 
ments of the ripples were seen on the sand forming the bottom. 
The formation of quicksands was illustrated by means of a tank containing 
ordinary sea-sand, and it was shown that when water was caused to flow 
upwards through the sand the latter acquired all the properties of a quicksand 
and swallowed heavy bodies placed thereon. 
The effect of obstacles lying on a sandy bed in the path of a current was 
demonstrated by means of a model. Stones and models of piles were placed on 
sand in the path of a current in a small tank, and localised erosion around the 
obstacles resulted in each case. This was shown to be due to the deflection and 
increased local velocity of the current. 
The curious effect of suspended matter on the specific gravity of water was 
illustrated by means of a glass cylinder containing water in which sand was 
shaken up; it was shown that, while the sand was suspended, the specific gravity 
measured by a floating hydrometer was raised above that of water. The 
influence of such a rise in specific gravity in increasing the intensity of impact 
of the water and consequently its erosive power was indicated. 
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