216 EEPOET OF THE COMMISSIONER OF FISHERIES. 



appeared. B. coli is found onl}^ occasionally, and then on the ebb 

 tide. Another zone of pollution spreads out from Warren River, 

 however, and at station 1, buoy No. 1, 3 miles below the town of 

 Warren, evidences of it can be discovered; but at station 6, 4 miles 

 below this town, examination fails to reveal the presence of sewage 

 bacteria. Samples from the Prudence Island and Wickford oyster 

 beds contained no colon bacilli; neither did the samples collected over 

 the southern parts of the Rocky Point oyster ground, so that the 

 Providence River, 8 miles below the chief sources of contamination, 

 ceases to be a polluted stream. If sewage is present in the water below 

 this point, it is in too great dilutions to be recognized in the 1 c. c. 

 samples that were used in this work. The waters of Narragansett 

 Bay are also free from sewage pollution. 



The next series of samples was collected in or near the Kickemuit 

 River. Three stations were located in this part of the ba}-: Station 1, 

 over the oyster layings south of Warren Neck; station 2, just inside 

 the mouth of the Kickemuit River; and station 3, aljout three-quarters 

 of a mile farther up the river, B. coll was found in but one sample 

 from the oyster beds south of Warren Neck, which are 4 miles from 

 the Fall River sewer. Finally, three stations near the entrance to 

 Mount Hope Bay were visited — stations 1 and 2, over the oyster bed 

 north of Common Fence Point, 6 and 6f miles, respective!}", from Fall 

 River; and station 3, over the Bristol Ferry bed, 1\ miles below the 

 city. But a single sample contained the colon bacillus. This was 

 collected at station 3, otf Bristol Ferr}^, and the presence of the organ- 

 ism was probabl}^ due to some local contamination rather than to the 

 sewage from Fall River, since samples from stations 1 and 2, consider- 

 ably nearer the chief source of pollution, did not contain this bacillus. 



As a final test of the distribution of sewage bacteria in the river, an 

 attempt was made to estimate the number of colon bacilli per cubic 

 centimeter in this water. For this test lactose agar plates containing 1 

 per cent neutral red were inoculated directly wdth the water to be 

 tested, and incubated forty-eight hours at 42° C. After this period, 

 the colonies developing were examined, and those exhibiting the char- 

 acteristic appearance of B. coll on this medium were counted. It was 

 impossible to study each separate colon}" in pure culture, therefore 

 these figures have but an approximate value. Four plates were made 

 from each sample; and the figures given in Table VII represent the 

 average number of characteristic colonies developing within the given 

 time. The samples used in this test were collected (October 21, 1901, 

 tide rising) at the stations indicated on the map on page 203. The 

 first sample was taken near the sewer outfall at Fields Point; the 

 others at places farther down the river. 



