150 



by any increase. Indeed, the average level for this month at 

 Copperas Creek is only 2.82 feet, the lowest average for the 

 year. The rises attending this period appear but twelve times 

 in twenty-one years, are usually insignificant, and are often less 

 than two feet, owing doubtless to the greater capacity of the soil 

 for absorption at this season of the year. 



The time not included in the high- and low-water periods 

 as here defined amounts on the average to 96 days, a relatively 

 short time for the transition between these two extreme condi- 

 tions. This abruptness of the transition stages is to some ex- 

 tent apparent in the hydrographs. 



On Tables I. and II. will be found tabulations of the total 

 movement, both -f and — , of the river levels in each month in 

 the period covered by the records at the two dams. The 

 monthly and yearly averages of these data are also given. The 

 figures are to a certain extent an index of the relative stability, 

 both monthly and annual, of the river. The averaging process 

 has to some degree masked the differences in the several 

 months, as will be seen on a comparison of the mean monthly 

 movements with those for any single year, the latter exhibit- 

 ing at some times of the year much greater contrasts than the 

 means. Thus the greatest and least movements in 1897 are re- 

 spectively 10.37 feet in January and 0.40 in October, while the 

 corresponding limits in the means are 4.18 feet in July and 2.78 

 in November. The means indicate two periods; one of consid- 

 erable movement, corresponding to that of high water, and one 

 of less movement, representing the low-water stages. The 

 greatest movements occur in February and July, indicating the 

 rise and decline of the flood. The least movement is found in 

 November, a period of low water and freedom from sudden and 

 heavy rainfall. The several years exhibit quite a range in the 

 total amount of change in levels, the extremes in Copperas 

 Creek in twenty-one years being 68.70 feet in 1881 and 32.92 in 

 1894; at La Grange, in seventeen years, 85.36 feet in 1898 and 

 40.41 in 1887. The movement is thus somewhat greater and 

 more variable at the lower dam, In general there is some cor- 



