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should not be introduced twice. A good apprcximation of the final 

 foirn of the offshore tide generator components can be obtained 

 from a weighted average of the tidal coefficients at stations 

 offshore or some distance away in both directions along the coast. 



The complexity and rate of going of a tide generator varies 

 with the character of the tidal trace both within and along the 

 seaward margins of the prototype. The canponents of a tide 

 machine are determined fran the relative importance of each of 

 the several tidal coefficients compared with their sum. Unimpor- 

 tant coefficients of the same tidal species can be collected and 

 introduced as a single component driven at the weighted mean 

 rate. Important species having speed numbers sufficiently close 

 to this weighted mean can be added as well to siraplify the mechan- 

 ism. Separate components must be set apart if their amplitudes 

 and speed numbers are such that they largely determine the char- 

 acteristic sequence of tides. In middle latitudes near open sea 

 coasts, the tides are predominantly semi-diurnal with more or less 

 diurnal inequality and a semi-monthly sequence of ranges. If 

 neither the diurnal inequality nor the semi-monthly range sequence 

 is large, the tide can be closely approximated by a single drum 

 of the proper displacement driven at the weighted mean rate of 

 all the significant semi-diurnal species known for that station. 

 If the diurnal inequality is too groat to be neglected but the 

 diurnal species are still unimportant, two serai-diurnal drums 

 will suffice. If the diurnal species are important, and have a 



