History of the Science of Ilydraidics. 201 



bank a little less than 0.1 of a foot above its level at the 

 opposite side of the river. In the proceedings of the American 

 Association for the Advancement of science for 1848 and 

 1849, are valuable papers, which contain the results of experi- 

 ments made at Natchez and Memphis upon the Mississippi 

 river. The daily discharge at Memphis was' determined by 

 making a cross-section of the river, and subdividing it into 

 three partial areas. The surface velocity in each of these areas 

 was measured by anchoring the boat and using a chip and 

 line. During calm weather the relative velocity near the 

 bottom was also measured by comparing the velocity of a sur- 

 face float and a double float whose lower portion, composed 

 of a tin vessel, was sunk nearly to the bottom. The discharge 

 was equal to the sum of the products of the partial areas by 

 the average velocities in them. The temperature of the water 

 at the bottom was found to be the same as at the surface. 

 The velocity near the bottom was to that at the surface in the 

 ratio of 268 to 300. The average downfall was 0.11 inches, 

 and the average evaporation from the surface of the water of 

 considerable depth, was 0.13 inches daily. 



Mr. Ellet, in a memoir to the Smithsonian Institution in 

 1849, advocated the reservoir system for the improvement of 

 the Ohio and other rivers. M. Boileau made a very extended 

 series of hydraulic experiments by order of the French gov- 

 ernment between the years 1844 and 1854, which were pub- 

 lished in the last mentioned year. It is a work of great value 

 to the science. 



In 1851 Mr. Ellet submitted a report to the War Depart- 

 ment upon a survey made by him under its direction to deter- 

 mine the best method of preventing the overflows of the delta 

 of the Mississippi. In the same year appeared a work on 

 hydraulics by M. de Saint Venant, which contains much 

 origmal and valuable matter. In 1855, Herman Ilaupt pub- 

 lished a pamphlet advocating the improvement of the Ohio 



river, by a low dam and chute plan. Lombardini, in 1858, 

 14 



