50 TRANS. ST. LOUIS ACAD. SCIENCE. 



whether it is adapted to the comparatively shallow water of the 

 river above Cairo, but its efficiency may well be doubted where 

 the water is deep.. 



We have no means of ascertaining the first cost of such work, 

 but, even if much cheaper than the first method, it cannot be 

 considered the cheapest until tested by comparison with other 

 methods. Furthermore, the system now under trial construction 

 can only go on during low water, and, judging of its stability by 

 that of Alton Slough, it is doubtful if it is possible to make a 

 work of the kind permanent in the strong currents of the Missis- 

 sippi between the mouth of the Missouri and Cairo, and still more 

 doubtful below Cairo. 



- The next plan proposed is that of Captain Eads, which may 

 properly be called the concentrating theory combined with the 

 lengthening. 



Mr. Eads's plan is to narrow the wide places in order to con- 

 centrate the water and cause it to cut a deeper bed for itself. 



Mr. Eads makes no provision against the lengthening of the 

 river. He claims that the narrowing of the channel at the shoal 

 places, and the consequent deepening, will accomplish the pre- 

 vention of overflow. 



In examining this plan we find that Capt. Eads does not take 

 into account the gradual lengthening of the river consequent upon 

 the more rapid destruction of the banks now than formerly. It 

 is a well established fact that the length of the river from Cairo 

 to New Orleans has sensibly increased during the last fifty years. 

 Authorities do not agree on the actual increase, some reducing it 

 to 20 miles, whilst others make it over 50 ; but all agree that 

 there has been an increase notwithstanding there has been over 

 200 miles of shortening by "cut-offs," and leaving bends of 

 islands, and going through shutes (as at Paw-paw and 95). It 

 will be apparent to the most superficial observer, that, unless the 

 lengthening of the river is taken into the calculation, the problem 

 will not be solved except temporarily. This one objection redu- 

 ces his system to a temporary expedient, and as such it should 

 be considered. 



The next is Captain Cowden's plan, or what may properly be 

 considered the scattering theory. 



