484 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Taking these points into consideration : — 



(1) The mussel-bearing area is relatively small, and 



the volume of sewage entering it is relatively 

 large ; 



(2) The pollution is recent; 



(3) The conditions of the industry; 



(4) And the high bacteriological impurity; 



we must conclude that the mussels between the 

 Perch, at the mouth of the Estuary, and the upper beds 

 are at present objectionable articles of human food. 

 The mussels from the scars and channel at the mouth of 

 the Estuary, seaward from the Perch, are far less liable 

 to dangerous pollution. But as the industry has been 

 conducted during the last few years it has been 

 practically impossible to distinguish between the mussels 

 from these two parts of the whole area, since all may be 

 washed and stored in the river near to the principal 



2. The Estuary of the Lune. 



It is far more difficult to express an opinion with 

 regard to this area. The volume of the Estuary is much 

 greater than that of the Conway, nevertheless it is a 

 relatively narrow strip of tidal water, artificially 

 contracted by training walls, and there is no escape 

 for the sewage : it must mix with the estuarine water. 

 The dilution of the sewage is very great : it is estimated 

 that the volume of water passing up and down the estuary 

 on each tide is about 2,769,000,000 cubic feet, while that 

 of the sewage nowing in during the same period is about 

 220,000 cubic feet. The dilution is therefore ish^u- 

 The flood tide enters the estuary from the open sea and 

 therefore consists of practically unpolluted water. 



