151- TRANSACTIONS OF THE CANADIAN INSTITUTB. [VoL I. 



for surface waters, have till very recently supplied the great bulk of drink- 

 ing water both in towns and country districts. Now in every instance the 

 same laws are in force, and we have seen that they involve: — (]) A 

 downward force of gravity ; (2) a hindrance such as an impervious 

 stratum ; (3) a lateral movement of ground-water towards the lowest 

 attainable point, whether this result in great subterranean water-beds on 

 the rock strata, supplying conditions for artesian wells ; whether in the 

 appearance on the hill sides of gurgling springs and a saturated surface 

 soil in the vicinity, or whether in the soakage into the nearest depression, 

 as wells, cellars or other shallow excavations of waters, all following the 

 general law of downward and lateral movement where obstructions do 

 not prevent. 



We have now reached the second and more important part of our sub- 

 ject, and the subject to which I have more especially devoted this study, 

 viz., the constitution of ground-waters. 



2. — CONSTITUTION OF GROUND-WATERS. 



In addition to the chemical combination of hydrogen and oxygen 

 making pure water, we are aware that a large number of other chemical 

 compounds are held in solution by it, and that in its passage through 

 the soil it dissolves out such soluble matter as it comes in contact with. 

 We may hence speak of the chemical constituents of ground-waters as 

 impurities, although, as we know, they owe to the mineral salts in solu- 

 tion their agreeable and wholesome qualities. These impurities, with 

 minute amounts of organic matter, which from their occurrence indepen- 

 dently of all adventitious influences may be called obligatory in contradis- 

 tinction to the facultative or inconstant impurities which depend upon 

 influences which may be removed I do not propose to refer to further 

 here, but shall limit our study to the facultative impurities of an organic 

 character. 



Everyone is aware that water will carry in suspension, as in rivers, 

 ponds, etc., very large amounts of organic materials, and that from these, 

 whether animal or vegetable, it abstracts soluble matters, remaining 

 present until decomposed into simpler constituents. To give but one 

 illustration, the City of St. Louis, Mo., has four settling basins, holding 

 18,000,000 gallons of water. Their floors are paved with brick, and upon 

 these are deposited by sedimentation the suspended, and to some extent 

 the dissolved materials of the river water. Once in five months the 

 sediment is flooded out of the reservoirs, and the quantity thus removed 

 is nearly 200,000 yards, of course of largely inorganic mr^tters. This is 

 when the needs of the city allow only of sedimentation going on from 



