SEWAGE CONTAMINATION OF OYSTER BEDS. 229 



river were infected. Seventy-four per cent of the water samples 

 taken ov^er the Sabins Point ojster ground, directly across the river 

 from Pawtuxet, gave positive tests for B. coll. Seventy per cent of 

 the oysters from this ground contained this organism within their 

 shells. 



Fifty-nine per cent of the water samples taken over the Bullock 

 Neck oyster beds, 2 miles below Sabins Point, contained B. coll. 

 This organism was isolated from .53 per cent of the oysters obtained 

 from this locality. 



Fifty per cent of the water samples collected on the Conimicut 

 Point oyster beds, but only 32 per cent of the oysters from this source 

 contained B. coll. 



Off Nayatt Point, 5i miles south of Fields Point, the water is much 

 freer from sewage pollution. Thirty -one per cent of the water sam- 

 ples and only 23 per cent of the oysters taken from this part of the 

 river contained coloa bacilli. 



The Warren Kiver, however, is a polluted stream, B. coll being fre- 

 quently found in a series of samples taken at intervals from the mouth 

 of this river to the town of Warren; and also in a sample taken in 

 the Providence River in the flow of the tide from the Warren River, 

 though this pollution is soon swallowed up in the larger volume of 

 the Providence River, so that no trace of B. coll can be found 2 miles 

 distant from the entrance of the Warren River. The bacillus was 

 found in over 60 per cent of the oysters taken from the Warren River 

 beds. 



On the western side of the river, 6 to 8 miles below the sewer out- 

 let, B. coll is found only occasionally and then on a falling tide. It 

 was present in only one oyster from this section of the river. 



From the above data it may be noted that the zone of sewage pol- 

 lution of the Providence River reaches southward from the Fields 

 Point sewer outlet for a distance of about 6 miles. 



In Narragansett Bay proper a different set of conditions exists. 

 The western passage is free from sewage pollution, and neither the 

 water nor oysters at Prudence Island or Wickford are infected with 

 the colon or other sewage bacteria. 



The Fall River sewer is, of course, the principal source of contami- 

 nation of the waters of Mount Hope Bay, but it is at least 4 miles 

 away from the nearest oyster bed, and the water and 03^sters from the 

 Kickemuit River are not found to be infected with any sewage bacteria. 

 In the sample from the Narrows, the entrance to Mount Hope Ba}^, 

 B. coll was found in a single instance. Two oysters from the beds 

 situated off the shore of Bristol Ferry were infected. 



