168 TRANSACTIONS OF THE CANADIAN INSTITUTE. | Voi.. 1. 



Of course there had been no time for polluting the soil and this was prob- 

 ably common sub-surface water. It shows however that the field, some five 

 acres in extent, was capable of absorbing more than 100,000 gallons 

 daily without supersaturation in dry weather. A letter received to-day 

 from Dr. Beemer says so far the farm, during this whole winter, shows 

 no surface collection of a notable character, although the soil as we know 

 has everywhere been in a condition of almost complete and constant 

 saturation. 



Now, without making any positive statements, I think that as regards 

 this w^hole matter of natural waters we may fairly draw the following 

 general conclusions : — 



1. That while the atmosphere as compared with the soil is relatively 

 free from bacterial life, yet rain-water bears to earth from the air and 

 gathers from the roofs, etc., the elements of auto-contamination, and finds 

 in the organic matters gathered from roofs, etc., abundant nutriment for 

 them. 



2. That falling on the surface of the ground waters become loaded 

 with bacteria of the soil, whether those indigenous to it or which have 

 been borne to it from a distance. 



3. That of these contaminated waters about 50 per cent, are not ab- 

 sorbed but follow the surface inequalities into brooks and thence into 

 the larger streams and great lakes. The brook as it passes through 

 virgin soil collects much albuminoid matter which affords abundant 

 nutriment for microbes, borne into it from every side, and when the 

 stream reaches a part where barnyards, and other sources of sewage 

 pollute it, it is likely — nay, certainly will — become contaminated with 

 bacteria of a dangerous character. 



4. Where gathered into the great lakes, deep and hence very cold, with 

 constant aeration going on and constant exposure to sunlight of their 

 great areas, there follows a great diminution in the bacteria of the water 

 through a lessening of the organic nutriment for microbes, and hence a 

 great halt in their multiplication, owing to the low temperature, aeration 

 and exposure to sunlight. 



5. Rivers, shallow lakes and bays along the great lakes, and these 

 especially during those periods when, by evaporation, their volume is 

 so greatly diminished by evaporation, are likely to become very impure 

 and the causes of their impurities are likely to remain more or less 

 permanent- 



6. The fifty per cent, of rain water which is absorbed by the soil 

 has a different history. Loaded with impurities in the upper layers of 



