44 TRANS. ST. LOUIS ACAD. SCIENCE. 



Curves modify velocity, and scouring is advanced or retarded 

 by the tenacity of the sides and bottom. 



These few simple factors cover the whole gi-ound of river im- 

 provements, land reclamation, and the sanitary conditions of the 

 Mississippi valley. I shall endeavor to point out how the differ- 

 ent factors act, and to show their effect. 



The following data, compiled from Humphry and Abbott's 

 reports on the Mississippi River, will illustrate the effect of fall, 

 volume, and curves, on velocity : 



The fall of the Mississippi from St. Louis to the Gulf of Mex- 

 ico is, in high water 408 feet, and in low 369. The air-line dis- 

 tance is about 700 miles, and by the river 1300. This gives 0.31 

 foot fall to the mile in high and 0,38 in low water. It is obvious 

 to all that if this distance (1300 miles) is increased or diminished, 

 the ratio of fall is diminished or increased in proportion. 



From St. Louis to Cairo (173 miles) the fall in high water is 

 86 feet and in low water 100 feet (14 feet more in low water than 

 in high). 



From Cairo to Columbus (21 miles) the fall in high water 

 is 12 feet and in low 8 feet (4 feet more in high than in low 

 water). 



From Columbus to Memphis (204 miles), 89 feet in high and 

 82 in low water (7 feet more in high than in low water). 



From Memphis to Natchez (494 miles) the fall in high water 

 is 155 feet and in low water 166 feet (11 feet more in low than 

 in high water). 



From Natchez to Carrollton (275 miles), 50.7 feet fall in high 

 water and 8.1 feet in low (42.6 feet more in high water than in 

 low). 



From Carrollton to the Gulf (104 miles), 15.3 feet in high and 

 0.9 of afoot in low water (14.4 feet more fall in high than in 

 low water). 



An examination of the foregoing facts shows two paradoxes 

 that are easily explained by a knowledge of the effect of volume 

 and curves. From St. Louis to Cairo and also from Memphis to 

 Natchez the fall is greater in low water than in high (14 feet in 

 the first and 1 1 feet in the second), and, if the friction on the bot- 

 tom and sides of the lesser volume, with the greater fall, did not 

 modify it, the current would be a fraction over ^V greater in low 

 water than in high between St. Louis and Cairo, and over jV 

 greater between Memphis and Natchez. 



