24 
subterranean aqueducts. Later still, through sheer shortage 
and economy, we had had to draw upon the waters of our 
short, rapid (and polluted) rivers, but only had this been 
possible with the advance of science, which had enabled us 
to purify these waters, and so amend our supplies to our ever- 
increasing needs. 
Rain and snow waters were generally fairly pure, in that 
they only contained dissolved atmospheric gases ; but when 
they passed through atmospheres poUuted by our industrial 
smokes, and other effluvia, which were carried by the winds 
for miles and miles, and all manner of organic and inorganic 
matters absorbed by the clouds, rain waters were contaminated 
before they reached the earth. The nature of the land upon 
which the rains fell also conditioned the quality of the 
water, which now began to form our streams and rivers. 
Open lands, over which both man and beast were free to roam, 
offered further sources of contamination, but on enclosed 
areas for gathering, these causes of contamination were dis- 
pensed with in some degree. Then the nature of the land 
itself played another role. Land where vegetation had 
flourished offered the decomposing organic vegetable matters 
to the water ; whilst rocky mineral areas offered saline 
matters to the waters. These agencies thus produced a 
certain amount of pollution for the water which served as 
the food for the lower forms of animal and vegetable life. Of 
the waters which sank into the ground, as distinct from the 
river waters — these, because of longer period of contact, and 
meeting with more variety of earthy matter, became more 
heavily charged with both suspended and dissolved bodies ; 
and so we found the deep wells and the springs always to 
contain more solids than the surface waters. The consti- 
tuents of the various strata through which the water per- 
colated conditioned the nature of the saline contents of the 
water, and determined the composition and extent of 
the hardness of the water — which was a most important factor. 
Simultaneously with all these processes of addition to the 
water, we had the natural agencies at work for purification. 
Purification consisted essentially of an oxidisation or a moist 
combustion — that was, a striving of the forces of nature to 
resolve dead organic matter into mineral matter. This 
process was brought about by natural agencies, such as 
the lower forms of vegetable and animal life, and ended 
when there was nothing left in the water to support the exis- 
tence of those forms of life, whilst the gaseous oxygen of 
the atmosphere we breathed accomplished the final oxidi- 
sation. 
