SEA-FISHERIES LABORATORY. 445 



serving a population of about 200 people, and nearly 

 opposite this, on the Port Madoc side of the harbour, is 

 another outfall, No. 3, serving also about 200 people. 

 Lower down, and nearly opposite to the Ballast Bank, 

 is another outfall, No. 5, from which the sewage of about 

 380 persons is discharged. Lower down the estuary 

 still, at Amanda Terrace, at Borth, is an outfall, No. 6, 

 which drains an area populated by about 600 people. 

 This was the condition of the estuary, with regard to 

 sewer outfalls, in 1910. Since then a septic tank has 

 been constructed at Borth. 



The channel formed by the Glaslyn river below Port 

 Madoc is very shallow, and the depth of Avater in the 

 harbour is also very little. The bar at the entrance to 

 the channel is a high one, so that there is not much inter- 

 change of water between the harbour and the sea outside. 

 For four or five days before and after the lowest neap 

 tides water probably oscillates up and down the channel 

 between the harbour and the bar, and is not really 

 renewed from Tremadoc Bay. For a few tides at about 

 the time of the springs there will be a renewal of the 

 water from outside, but for most of the fortnight between 

 one high spring tide and the next one sewage probably 

 accumulates in the water of the harbour and channel, 

 and is then flushed out during the two or three highest 

 tides of each fortnight. A certain amount of Hushing 

 action is probably also produced by heavy Hoods coming 

 down from the upper parts of the Glaslyn river. Because of 

 these conditions samples of mussels and water taken 

 from harbour and estuary will give very different 

 bacteriological results, according to the state of the tide 

 when the samples are taken. I did not have time to 

 make a complete series of analyses at all states of tide 

 and river Hooding, but if mussel cleansing works should 



