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should not be introduced twice, A good approximation of the final 

 foim 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 ccniplexity 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 caaponents of a tide 

 machine are determined from 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 conponent driven at the weighted mean 

 rate. Important species having speed nvunbers sufficiently close 

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

 ism. Separate components must be set apart if their an^jlitudes 

 and speed nvimbers 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 displaceraent driven at the weighted mean rate of 

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

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

 diurnal species are still unimportant, two semi-diurnal drums 

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



