152 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
the probable drift of sewage, were worked out by 
Mr. Durlacher, and his results were given in last year’s 
Annual Report. By far the greater part of the sewage 
is discharged from the main sewer well outside the mouth 
of the Estuary, and this cannot affect the water at 
Aberamffra. But there is another broken sewer pipe 
discharging into the Estuary about a quarter of a mile 
below the Bridge, there are some privies on the quay- 
side, and there are drains from four houses on 
Aberamitra Cliff which discharge directly on the 
foreshore. These are the sources of contamination. A 
very unfortunate condition, affecting Aberdovey, 
Barmouth and Portmadoc, is the configuration of the 
Estuaries. Because of the sandbanks and the very 
shallow water on the bars, these are, to some extent, 
‘‘bottle-necks.”’ In each case the Estuary is wide 
above, and narrow at its mouth, and as a result there is 
not a complete change of water at neap tides. At 
Barmouth and Portmadoc the water in the upper parts 
of the rivers is probably changed completely during the 
springs, but at neaps only a part becomes carried out to 
sea. Some water therefore oscillates up and down 
between the bar and the upper reaches for several days, 
becoming charged with sewage all the while. This 
is less the case at Aberdovey than in the other two 
Estuaries, but it is still a matter to be considered. 
At Barmouth the flood stream takes the general 
direction indicated by the arrows drawn on the sketch 
chart. Water previously containing sewage flows close 
to Aberamffra, but does not enter the harbour directly. 
There is a slow eddy there which is roughly indicated on 
the chart. 
It might seem, therefore, that the proposed situation 
of the tank is such that it cannot avoid contamination, 
