4 bulletin 83. 
and other surplus waters in order to subsequently distribute them, 
that they might add to the well-being and prosperity of those liv¬ 
ing in sections further down the stream, but our agriculture has 
so increased that much more water is required than formerly, and 
in order to meet this requirement our reservoir systems have con¬ 
stantly grown. All available sources of water are rapidly being 
made to render service, until the waters of the mountains are 
taken out of the streams and returned several times, before being 
finally discharged into the bigger streams of which their natural 
channels or smaller streams are confluents. We may yet learn to 
•r mf 
further increase the duty of water, but if we do we will not lessen 
the questions relative to the changes produced and suffered by 
these waters used for the purposes of irrigation. We will, on the 
contrary, intensify them and probably find that new questions 
will be raised. . 
It is well known, but still more generally accepted as a fact, 
that the waters of rivers rising in high mountains where there is 
little soil, a scanty vegetation and no human beings to pollute 
them, are comparatively pure, many of them very pnre indeed. 
This is the case with the waters of our mountain streams and is 
not a fancy arising from the notions which we associate with the 
mountains and their seclusion. The rocky face which their sur¬ 
face so generally presents does not wholly withstand the attack, 
gentle though it seem, of the falling rain or melting snow. The 
rocks yield little by little it is true, but the water is never able to 
enrich itself greatly in mineral matter at their expense. The 
work done by the waters in a year, a month, or even in a week, 
when measured in the aggregate is surprisingly large, but no 
given quantity of this water, a gallon or so, carries more than an 
infinitesimal part of the product. This water is usually colorless 
and free from organic matter because we have no accumulation of 
decaying organic matter such as peat, etc. to contaminate it. Where 
the surface is covered with soil there is little difference between the 
soil and the rocks on which the soil rests. I do not know whether 
the changes which take place in this soil proceed more rapidly than 
in the rocks proper or not; it is presumable that they do, but they are 
essentially of the same kind and this is true throughout the moun¬ 
tain region. These waters suffer little change so long as they 
continue to flow over the rocky beds which they have cut for 
themselves in the flanks of the mountains, or so long as they 
move through the soils which are little more than the pulverized 
rock on which they lie. This, however, is no longer true when 
they issue from the mountains and enter the plains. 
We think of water flowing in a stream as being the same 
water that it was at its source. I11 a certain sense it may be, but 
if we apply this to mean that the water in onr streams after they 
