ELECTHiC P0WI:R from the MISSISSIPPI RIVER CLARK. 203 



The river in its natural condition at this place is about 2,600 feet in width at 

 ordinary low water and about 5,500 feet in width at flood stages. The bed of 

 the river is limestone, of the same character as that of the whole Des Moines 

 Rapids, which extend from this place to Montrose, about 11 miles. 



On page 313 of Report of the Chief of Engineers, United States 

 Arm}'-, for the year 18G7, is found a description of the Des Moines 

 Rapids, in which the following extract appears: 



This erosive action, though productive of such remarkable results, has not 

 been carried sufficiently far to render the river through this part of its bed, 

 available at all times for the purposes of navigation. From Fort Madison to 

 Montrose, the river is about 2,500 feet wide, and sufficiently deep ; but in the 

 rapids its bed of limestone rock, which by some unknown cause seems to have 

 been hardened to a greater degree than the corresponding stratum above and 

 below the rapids, has resisted the action of the water, while its sides have given 

 way. The result is that this mass of rock remains there, acting exactly as an 

 artificial dam whose upper surface slopes about 22 feet in 11 miles, and con- 

 forms very nearly to the plane of stratification of the rock through which the 

 channel is cut. The bluffs extend along the banks of the river throughout the 

 length of the rapids, presenting a rock escarpment at the present high water- 

 mark with a sloping gravel beach to low water, and also another escarpment 

 of rock at 105 feet above the present water level, having, likewise, a sloping 

 beach at its foot. 



FLOW OF RIVER. 



Readings of the stage of the Mississippi River at various points 

 have been made by the United States Government since 1868. These 

 readings have been published as part of the records of the Missis- 

 sippi River Commission and of the United States Weather Bureau. 

 Besides reading the stage of the river the Government has, through 

 the United States Army and the Mississippi River Cormiiission, ob- 

 served at various times and at various points the discharge of the 

 water. 'The results of these discharge measurements also form part 

 of the records of the Mississippi River Commission as well as of the 

 United States Engineers. In addition to these, various observations 

 have been taken under the direction of Mr. Cooper. For the purpose 

 of determining the amount of power available all of the above ob- 

 servations, and particularly those establishing a minimum flow, have 

 been valuable. So far as is known to the engineers of the develop- 

 ment, the lowest measured discharge was recorded by Montgomery 

 Meigs, United States Civil Engineer, in September, 1891, when at a 

 time that the commonly accepted low-water marks on Mechanics' 

 Rock, just above Keokuk, showed water lower than the record of 1864, 

 there was observed a discharge of 21,389 cubic feet per second. Other 

 observations of minimum discharge are shown in the tables which 

 follow, being the lowest records of which the engineers of the de- 

 velopment have authentic knowledge. 



