COLORADO IRRIGATION WATERS AND THEIR CHANGES. 69 
stream, even to the distributing furrows in the fields. The analysis 
of this material gave the following results: 
TABLE LVIII. — ANALYSIS OF SUSPENDED MATTER IN 
WELCH DITCH, SAMPLE TAKEN ONE MILE ABOVE 
GOLDEN, AUGUST 27, 1902. 
PER CENT. 
Silicic Acid.5:1.991 
Sulfuric Acid, Sol. in HC1..... 0.064 
Sulfur . 1.908 
Ferric Oxid. 9.420 
Aluminic Oxid . 15 822 
Manganic Oxid. 0 636 
Calcic Oxid. 1015 
Magnesic Oxid. 1.613 
Zinc. 0.383 
Copper. 0 201 
Lead. 1 214 
Potassic Oxid.. 4 650 
Sodic Oxid. 1.057 
Loss at 60°. 2.386 
Loss above 260°. 5.495 
Total.9iK?75 
Nitrogen 0.121 per cent. 
PJF § 131. The suspended matter amounted to 0.149 per cent, 
of the weight of the water, equal to 4,056 pounds per acre foot, 
carrying 4.9 pounds of nitrogen and .190.6 pounds of potassic oxid. 
This mud is richer in these elements of plant food than the mud 
of flood waters. The lead, copper and zinc found indicate the 
presence of 1.402 per cent, of galena, 2.502 per cent, of pyrites, 
0.517 per cent, of sphalerite or zinc blende and 0.581 per cent, of 
chalcopyrite. These quantities of these minerals have escaped 
the concentrators and failed to be deposited before they reached 
this point. We have here to deal with a mixture of clay and fels¬ 
par, a conclusion entirely in harmony with the facts known con¬ 
cerning the concentrating ores in this district. 
§ 132. It appears from the results of the examination of 
these sediments, that they are composed essentially of the finer 
particles formed by the decay and comminution of the rocks form¬ 
ing the mountains, or rock particles forming the soil, which in our 
case amounts to saying the same thing. Our soils contain, as their 
mass analysis shows, a little over two per cent of potassic oxid, 
2.2 to 2.6. These sediments contain less than the soils, except in 
the case of the mud from Clear Creek, which contains about as 
much as ordinary granite, 4.6 per cent. These results confirm an 
opinion which I have long entertained, i. e., that there is danger 
of our overestimating the value of the silts carried by our streams, 
as it seems almost impossible for this silt to be other than it ap¬ 
pears to be from the study of the silts themselves, and the analysis 
thereof; namely, a mixture of the fine particles of the minerals 
constituting the mountain masses of the country. 
