COLORADO IRRIGATION WATERS AND THEIR CHANGES. 77 
conclusion that it is deposited in large quantities on the soil we have in 
mind. In this case the color and fineness of the sediment make a gen¬ 
eral impression of richness upon our minds, and we forthwith accept it 
as an established fact when it is not. The composition of this sediment 
does not justify the inference. 
56. This sediment, very naturally, resembles in composition the 
source from which it was derived, which was the soil of the mountain or 
hillsides and their valleys. These soils have a common source with 
those of the plains, and it is therefore, on reflection, no matter for 
surprise that the sediments should not be found to be richer than the 
latter. There are two respects in which the sediments, in some measure, 
differ from the soils on which they would be deposited in our case, but 
this measure is not very great. These two respects are the fineness of 
division and the amount of organic matter contained in them. The fine¬ 
ness of the sediment is a condition favorable to the alteration of those 
mineral particles containing elements of plant food, whereby these lat¬ 
ter are made available. The amount of organic matter contained is 
larger than in the average of our plains soil, but is not large when con¬ 
sidered by itself. The case resolves itself to about this, that the 0.04-inch 
of sediment, which an application of two feet of water to an acre of our 
soil would add, would be equivalent to adding a layer of the same soil 
only a little more uniformly fine and containing a little more organic 
matter. 
57. The sediments from the ditch waters are of the same character, 
and resemble more closely still, the soils to which they would be ap¬ 
plied with the water. 
58. Another sample of sediment examined was one which had been 
carried by flood waters and deposited as silt in a reservoir, the Queen 
reservoir, Prowers County, Colo. The mineralogical and chemical com¬ 
position of this suggests the same considerations, and points to the same 
conclusions that I have endeavored to set forth in discussing the sedi¬ 
ment carried by the flood water of the Poudre. This sediment, however, 
is less suggestive of the probability of any considetable benefit accruing 
to the land by its application to it. 
59. The fourth sediment examined was of an entirely different ori¬ 
gin, and naturally of a different character, and certainly ought to be 
looked at from two different and opposite points of view. The prac¬ 
tically more important one being in regard to the possible injurious 
effect which any minerals present in it might have upon the vegetation 
to which it might be applied with the water. The other point of view is 
the same as that from which we have briefly considered sediments car¬ 
ried by our streams in general. 
60. The analysis of the sediment answers the question relative to 
the presence of minerals, either injurious in themselves, or by the prod¬ 
ucts of their decomposition, in the negative. The amounts of sulphid 
of lead, zinc, copper and iron do not exceed 35 pounds per ton of sedi¬ 
ment, or if the whole of the sulfur found were present as iron pyrites, 
probably the most dangerous form in which it is likely to be present, 
the total amount would be 43 pounds per ton, about 86 pounds per acre- 
foot of water, a quantity, of itself small, and which can be reduced by 
the use of settling ponds, or other settling devices. 
61. From the second point of view the quantity is not only mate¬ 
rially in excess of the quantity carried by our streams in times of ordi¬ 
nary high water, but actually carries more potash, nitrogen and organic 
matter, the former constituting the principal value in either case. 
