632 BACTERIA IX AVATER. 



riological examination may prove to be of great value if it succeeds 

 in demonstrating the presence of certain pathogenic bacteria and in 

 thus preventing the use of a dangerous water. We do not mean to 

 say, however, that an enumeration of the bacteria present in drink- 

 ing water has no practical value. An excessive number indicates an 

 excessive amount of organic pabulum, which may have come from 

 a dangerous source; and the dangerous pathogenic bacteria are not 

 only more likely to be present in such water, but they can more 

 readily multiply in it, while in a pure water they would fail to in- 

 crease in number, and, as has been shown by experiment, would die 

 out within a short time. 



The number of bacteria present in rain water, or in snow which 

 has recently fallen, varies greatly at different times. Naturally the 

 number is greater when the surface of the earth is dry and the at- 

 mosphere loaded with dust by currents of wind passing over it, and 

 less when the surface is moist and the atmosphere has been purified 

 by recent rains. 



In snow from the surface of a glacier in Norway, Schmelck found 

 two bacteria and two spores of mould fungi per cubic centimetre of 

 water from the melted snow. Ganowski, in experiments made with 

 freshly fallen snow collected in the vicinity of Kiew, obtained the fol- 

 lowing results : February 2d, 1888 : temperature of the air, 7.2 C. ; 

 snowfall, 0. 1 millimetre ; number of bacteria in 1 cubic centimetre 

 of water from melted snow, 34 in one sample and 38 in another. 

 February 20th, 1888: temperature, 11.1 C. ; snowfall, 1.1 milli- 

 metres ; number of bacteria in one sample, 203, in another 384. 



Miquel obtained from rain water collected at Montsouri during a 

 rainy season 4. 3 germs per cubic centimetre ; in rain water collected 

 in the centre of the city of Paris, 19 per cubic centimetre. 



.HcuZhas also been shown to contain bacteria inconsiderable num- 

 bers. Bujwid found in hailstones which fell at Warsaw 21,000 

 bacteria in 1 cubic centimetre ; but this is exceptional, and is supposed 

 to be due to the fact that surface water had been carried into the air 

 by the storm and frozen. Fontin examined hail which fell in St. 

 Petersburg, and obtained an average of 729 bacteria per cubic centi- 

 metre of water from the melted hail. 



River water has been carefully examined by numerous bacterio- 

 logists in various localities and at different seasons of the year. We 

 give below some of the results reported : 



Water of the Seine at Choisy, before reaching Paris, 300 ; at 

 Bercy, 1,200 ; at Saint-Denis, after receiving the sewer water from 

 the city, 200,000 germs per cubic centimetre (Miquel). 



Water of the Spree beyond Kopenick, 82,000 ; two hundred steps 

 below the mouth of the Wuhle, 118,000 ; in Berlin above the mouth 



