i8 
BULLETIN 82. 
in the amount, but in the character of the mineral matter, which 
is perhaps best exhibited by the analytical results, showing that 
the silicic acid in the solid residue, has been reduced in percent¬ 
age, but almost exactly proportionally to the increase in the 
amount of total solids. The sulfuric acid has been increased 
nearly three times in percentage, and consequently a little less 
than nine times in absolute amount. The amounts of soda and 
potash have been doubled, but their percentages reduced, while 
the percentages of lime and magnesia have been greatly increased, 
and the absolute quantities are six and eight times greater. 
§ 33. The extent of this change will be more fully appre¬ 
ciated when we estimate the difference in the total quantity of 
solid matter carried by the stream in twenty-four hours, as we 
have done for the river above the mouth of the North Fork. We 
found that the river carried about twenty-six tons of inorganic 
material, or, assuming a specific gravity of 2.6 for the solid sub¬ 
stances, about 320 cubic feet. Assuming the same data to hold 
for the river water as it passes the Fort Collins water works ditch, 
we obtain from 65 to 87 tons, or from 800 to 1,067 cubic feet. 
Taking the higher figures, we discover an increase of 62 tons, or 
747 cubic feet of inorganic matter carried in solution. These 
figures represent the ratio of salts perfectly, and the actual 
amounts under the assumed flow, which, however, is too high for 
an average year. But if we take 150 second-feet, which is below 
the average, as the flow, it would still represent an increase of 31 
tons daily, or about 373 cubic feet of solid matter which enters 
the river in the section represented, about eight miles long. 
§ 34- It is evident that if a proportionate change takes 
place, as the water proceeds down the river it will soon be so 
changed that comparisons cannot profitably be made. In the case 
of our streams this is so greatly complicated by return waters en¬ 
tering the river and by direct flows being taken out for irrigation 
or storage that no attempt will hereafter be made to compare the 
results except as to some particular features. 
THE EFFECT OF STORAGE. 
§ 35. This problem is not at all simple, for the reason that 
the water collected in reservoirs is not all river water, and in order 
to present all the conditions faithfully a detailed study of the sup¬ 
ply would be necessary, which is clearly out of the question for 
me to make. I shall present analyses of some of our principal 
and older reservoirs which are, so far as I know, filled from the 
Poudre river and receive but relatively little seepage. The 
amount of seepage so far as I am informed, has never been de¬ 
termined. The amount of rain-water which they receive may be 
neglected. The concentration due to evaporation is not neg- 
