- 26 - 



strong semi-monthly sequence of amplitudes, or if the diurnal 

 species are less important but not negligible, three drums will 

 be required to produce an acceptable approximation of the tides. 

 This is the case applicable to Barataria Bay. 



The volume of water to be displaced in the model to effect 

 the rise and fall of tides is the volume ratio (Lj.^ ^r\ ^^®^ 

 the volume change (tidal prism) in the flooded areas of the proto- 

 type. To calciilate the displacements of the tide machine drums 

 it is possible to prorate the scaled volume of the tidal prism 

 among the important harmonic constituents in proportion to the 

 ratio of their amplitudes to the sum of all terms. This process 

 automatically includes and distributes the minor contributions of 

 the neglected components. 



The basic data for the Barataria Bay tide machine were taken 

 from 



1. Tidal Harmonic Constants (Atlantic Ocean) TH-1 Jan, 1942 

 U. S. Department of Commerce, Coast and Geodetic Survey 



2. Tide Tables (Atlantic Ocean) Ser. 671, 1946. 



U. S. Department of Commerce, Coast and Geodetic- Survey 



The two stations Pensacola, Florida and Galveston, Texas 

 distantly flanking Barataria Bay were chosen as a combination 

 which would be free of conspicuous estuarine resonance and the 

 average signatures of which would be indicative of the charac- 

 teristic tidal oscillations on the proximal parts of the conti- 

 nental shelf of the Gulf of Mexico. The average of the two sets 



