THE DELTA OF THE MISSISSIPPI RIVER 353 



On page 2697 of the same report the commission itself con- 

 firms Mr Ockerson's statement by its own opinion, as follows : 

 " The main object of this resurvey was to elicit some information 

 bearing u))on the question of the stability of the land about the 

 mouth of the river. In the rei)ort of Assistant Engineer Ocker- 

 son, appended to the report of the secretary, a number of figures 

 and comparisons are given, based u[)on this survey and prior 

 ones, indicating a progressive depression of the alluvial delta near 

 the mouth of the river." An interesting diagram, designed to 

 show the clianges referred to, assumes tliat either the tide gauge 

 had gone down or the level of the Gulf had gone up over one 

 foot in twenty years. Numerous pertinent facts might be brought 

 forward to show, in addition to the above, that the lands had 

 gone down and that the Gulf level had not changed. It is a 

 fact well known to people living in the delta of the Mississippi 

 that large tracts of land were long ago abandoned in consequence 

 of overflow by Gulf waters, due to the sinking of the lands. 



The conditions are very different now from those existing prior 

 to the construction of levees. There are at present no annual 

 accretions of sedimentary matters from the periodical overflows 

 of the river. These accretions formerly were a little more than 

 equal to the annual subsidence of the lands. 



As to the question of the rising of the Gulf level, careful inves- 

 tigations and inquiries around the entire Gulf coast from Yucatan 

 to Florida disclose no indications of any sucli elevations. The 

 factors in forming the great hydraulic conditions of the Gulf op- 

 erate so steadil}^ from year to year and from cycle to cycle that 

 we should naturally expect that, with the exception of small an- 

 nual changes due to wind and tides, the mean surface of the Gulf 

 would remain practically at the same level. The difference in 

 precipitation, fluvial discharge into the Gulf, and evaporation is 

 very slight as compared with the great current forces that make 

 and maintain tlie Gulf level. From very careful observations, it 

 may be stated that the mean precipitation, river discharge, and 

 evaporation amount, all told, to a little over three cubic miles 

 per day. This volume " sinks into utter insignificance when com- 

 pared with that produced by the inflowing current of the Yuca- 

 tan channel, which, according to a calculation from Tjieutenant 

 Pillsbur3''s current observations, hurls the enormous quantity 

 of six hundred and fifty-two cubic miles of water per day into 

 the Gulf."* 



*See a paper by A. Limlenkolil, Assistant U. S. Coast ami Geodetic Survey, in Science, 

 N. S., Vol. iii, No. 00, February 21, lH9(i. 

 24 



