SEWAGE CONTAMINATION OF OYSTEE BEDS. 



211 



Table II. — Analysis of water samples collected off Pomham. 



Date and station. 



Februcaij 26, flood tide. 



Station 1, .surface tube 



deep tube 



2, surface tube 



deep tube 



3, surface tube 



deep tube 



March ;?, tide falling. 



Station 1, surface tube 



deep tube 



2, surface tube 



deep tube 



3^ surface tube 



deep tube 



March — , tide fulling. 



Station 1, surface tube 



deep tube 



2, surface tube 



deep tube 



3, surface tube 



deep tu^be 



Dextrose 



fermented. 



Red colo- 

 nies on lit- 

 mus lac- 

 tose agar. 



-t- 



(") 



-t- 

 -f- 



B.coli. 



Other fecal 

 bacteria. 



" Not made. 



The data giv^en in Tables I and II «how clearly that the water of the 

 riv^er in the immediate neighborhood of Fields Point and also at Pom- 

 ham, li miles below this point, is polluted by sewage to a ver}^ con- 

 siderable extent, since it is possible to isolate B. coli from practically 

 ever}" sample collected within this area. This statement seems to be 

 trustworthy whether the tide is making upstream or falling, or 

 whether the samples are collected when there is a stiff breeze from the 

 southerly direction, thus tending' to drive an increased amount of 

 water up the river, or during a flat calm. 



An attempt to estimate the number of bacteria per cubic centimeter 

 in the water about Fields Point was made by inoculating nutrient gel- 

 ati/i plates from two of the samples collected April 10 and keeping 

 them three daj's at room temperature. Four plates were made from 

 each sample, and the average count of colonies developing was esti- 

 mated as follows: Station 2, surface water, 1,500,000 bacteria per 

 cubic centimeter; station 3, surface water, 2,000,000 bacteria per cubic 

 centimeter. Thus the quantitative as well as qualitative analysis 

 points to high organic pollution of these waters. 



The second series of samples was collected from a section of the 

 river from 2 to 2^ miles from Fields Point. These samples were taken 

 at five stations, as follows: Station 1 over the northern part and sta- 

 tion 2 at the southern end of the oyster grounds ojff Sabins Point; 

 on the Pawtuxet shore, station 3 in the shallow water covering the 

 sand beach west of the Rhode Island Yacht Club house, station 4 off 

 the end of the club wharf, and station 5 in shallow water again, from 

 the shore near the end of Pawtuxet Neck. Four trips were made to 

 the first two of these stations; but one to those on the western shore 

 of the river. The result of these analyses is included in Table III. 



