222 ELEMENTS OF WATER BACTEEIOLOGY 



expected. Suddenly, however, the tests became positive 

 and so continued for several days. On investigation it 

 was found that some of the wells had been taken up to 

 be cleaned, and that the workmen in resinking them had 

 used the water of the brook for washing them down. 

 This allowed some of the brook-water to enter the system. 

 It was also found that at the same time the water in the 

 brook had been high, and because of the lack of packing 

 in certain joints at the top of the wells the brook-water 

 leaked into the suction main. The remedy was obvious 

 and was immediately applied, after which the tests for 

 Bacillus coli once more became negative. During all 

 this time the chemical analysis of the water was not 

 sufl&ciently abnormal to attract attention. On another 

 occasion a water-supply taken from a small pond fed 

 by springs, and which was practically a large open well, 

 began to give positive tests for Bacillus coli, and on 

 examination it was found that a gate which kept out 

 the water of a brook which had been formerly connected 

 with the pond was open at the bottom, although it was 

 supposed to have been shut, thus admitting a contam- 

 inated surface-water to the supply." Whipple also 

 calls attention to the report on the Chemical and 

 Bacteriological Examination of Chichester Well-waters 

 by Houston (Houston, 1901), in which the results of 

 chemical and bacteriological examinations of thirty 

 wells were compared. It was found that the bacteri- 

 ological results were in general concordant and satis- 

 factory. The wells which were highest in the number 

 of bacteria showed also the greatest amount of pollu- 

 tion, as indicated by the numbers of B. coli, B. sporo- 



