MICROORGANISMS IN WATER 261 



Snow. — The results obtained from snow are similar to those ob- 

 tained from rain; but as a rule the numbers are larger, a result doubtless 

 due to the larger particles of the snow flakes. One investigator has 

 found from 334 to 463 bacteria per c.c. of snow water. On the sum- 

 mit of high mountains snow is practically sterile, Binot not finding 

 a single organism in 8 c.c. of water from mountain-top snow. 



Water issuing from glaciers is of remarkable purity, containing 

 only from three to eight organisms per c.c. ; but the numbers are larger 

 as the distance from the glacier increases. 



Hail. — Hail stones usually contain large numbers of bacteria, 

 varying from 628 to 21,000 per c.c. of water obtained from the melt- 

 ing hail. Fluorescing bacteria have been found in some samples; 

 and the presence of these microorganisms suggests that surface water 

 is sometimes carried up by storms and congealed. The presence of, 

 many molds in hail is due to contamination from the air. 



Deep Wells. — Deep well water and spring water contain as a 

 rule but few organisms, usually less than 50 per c.c. on gelatin at 20°, 

 and less than 5 per c.c. on agar plates at blood heat. In a series of 

 tests of water taken direct from forty- three artesian wells, 152.4 M. 

 (500 feet) deep or more, the writer has found an average of 27 per 

 c.c. for the gelatin and 1.5 per c.c. for the agar counts. These tests 

 have extended over a period of several years; and water from deep 

 springs has given similar results. 



Shallow Wells. — The bacterial content of shallow weUs depends 

 greatly on their location and construction. Even in those well loca- 

 ted and constructed, the number varies with the amount of rainfall, 

 and is often large. In polluted wells, very high numbers of organisms 

 are found. 



Sedgwick and Prescott found from 190 to 8,640 bacteria per c.c. 

 in impolluted wells. 



In the same class of wells, Savage found from 10 to 100 per c.c. by 

 the blood-heat count, and 100 to 20,000 or more by the gelatin count. 



Sixty polluted weUs examined by the writer gave an average 

 gelatin count of 740 bacteria per c.c. ; and thirty-eight weUs which were 

 free of contamination gave an average count of 400 per c.c. 



Polluted wells often give counts approximating the higher numbers 

 mentioned above; but, of course, the character of the bacterial flora 

 is quite different. 



