318 



The Harmonic Analysis of Tidal Observations 



Table 35. Computation of the range of the tide at Casablanca 

 on 29 March, 1939, at 11 h 30 min G. M. T 



about 1400 high and low waters and an experienced computor, considering only 

 the most important partial tides, can at the most in one year complete the pre- 

 dictions of only a few harbours. Therefore, for the sake of economy 



ft 



St 



rx; 



') 



TT 



Figs. 128, 129. Schematic drawing of a tide-predicting machine. 



as well as accuracy, the idea was conceived, only a few years after the 

 introduction of the harmonic analysis, to use a machine for these predictions. 

 Kelvin (1887) was the first to devise such a machine for computing the tides, 

 which later on was improved by Roberts (1879). The first machine built in 



