38 THE LMPROVKMKXT OF RIVERS. 



of the Arkansas River, and although the river was quite low, marking only 3.9 feet 

 on the gauge, it carried 761 grains of matter to the gallon, of which only 46 grains 

 was matter in solution (that is, the matter in suspension was g 'j by weight). 



" The matter in solution bears no constant relation to the volume of water, though 

 in a very general way it varies inversely with the volume of the water, and ranges from 

 ii to 70 grains to the United States gallon. The amount carried down, in this form, 

 from October, 1887, to September, 1888, was 6,828,350 tons. During the single month 

 of May, 1888, i, 1 6 1, 1 60 tons were carried out in solution. Taking the observations 

 for the entire year under consideration, the matter in solution is equal to about 0.31 

 of that in suspension. These relations, however, are not constant. In November, 

 1887, for example, the dissolved matter was more than six times as much as the sus- 

 pended matter while on October 13, 1891, the suspended matter was more than thirteen 

 times the matter in solution." 



(3) SLOPE. 



The slope of a river may be ascertained by leveling or by gauges set at known 

 elevations and read simultaneously. It varies greatly in different parts of a river and 

 at different stages in the same part, and even at similar stages at different times. 

 Local conditions govern it, and these conditions are always changing in rivers with 

 friable beds. When the water is low, the profile presents a broken outline; as it rises 

 this gradually changes, until at flood height the slope may be nearly uniform for long 

 distances, because it is not so closely affected by the bottom and by the banks. 



Gauges for Local Slope. The method of ascertaining the slope for use in gauging 

 operations is to make simultaneous readings, say at five-minute intervals, on a scries 

 of gauges erected at regular intervals of say 500 feet along the shore, for distances of 

 a half mile above and below the range-line or gauging section. The gauges arc usually 

 graduated to half tenths and can be read approximately by means of a vernier to 

 thousandths. They are inclosed in boxes which reach down 2 or 3 feet below the 

 water surface, and the water is admitted through a hole in the bottom, thus securing 

 the gauge from wave action. Where observers are not available for each gauge, the 

 readings are taken at longer intervals by a man passing along in a skiff as rapidly as 

 possible from the upper to the middle gauge, and another man from the middle to the 

 lower gauge, the middle gauge being read by each man and corrections made on all 

 readings as necessary. 



Observation of Daily Stages. -The recording of the stage of water in a river at 

 various points at the same hour every day will furnish useful information to those who 

 are engaged in the study of its improvement. For a complete and continuous record 

 of tidal stages there is in use a self registering, automatic gauge, but as a general tiling 

 observations on rivers are made by means of ordinary gauges, graduated in feet and 

 tenths, and placed with their zeros having reference to some established datum. These 

 gauges may be attached to lock- walls, brUjp-piers, tn-cs, or other fixed objects, and 





