71 



ure, the systematic variation sought for, and the amphtudes and 

 epochs derived by inference may be preferable to those determined 

 by direct analysis, particularly if the period of observations is short. 

 A considerable number of these small components are customarily 

 determined by inference. 



SUMMARY OF THE METHOD OF HARMONIC ANALYSIS 



132. The harmonic analysis of the tide at a station comprises: 



(a) Some six or more separate summations of the observed hourly 

 tidal heights for a period generally of 369 days to obtain the hourly 

 component heights of the S, M, and K group of components, and the 

 larger individual components (pars. 78 to 89). 



{b) The computation of Vq for each component at the initial hour 

 of the observations and of u at the middle of the period (par. 118). 



(c) The prelimmary determination of the epochs, k, and of the 

 amplitudes, R (corrected by the augmenting factor) of the compo- 

 nents of each group, and the larger individual components, from their 

 computed hourly component tidal heights (pars. 91-99, and 118), 

 and the preliminary inference of the remainder for use in elimination 

 (par. 130). 



(d) The elimination of the effect of one component on another 

 (par. 100). 



(e) The reduction of the corrected amplitudes to their mean values, 

 H (par. 127) and the final inference of the constants of the compo- 

 nents not analyzed. 



133. Standard forms to systematize these computations, and tables 

 giving the requisite data are published in the Manual of Harmonic 

 Analysis and Prediction of Tides of the United States Coast and Geo- 

 detic Survey. The labor entailed in the analysis of the tide at a 

 station is apparent. The dependability of the results of a tidal 

 analysis is illustrated by a comparison between the separate deter- 

 minations of the harmonic constants at Fort Hamilton, New York 

 Harbor, for three periods of 369 days beginning January 1, 1900, 1904, 

 and 1928, respectively. Omitting the constants derived by inference, 

 the determinations are as follows: 



