THE TIDES 



307 



and these simple harmonic con- 

 stituents added together give the 

 complicated tides. 



All the work hitherto done 

 has been accomplished by sheer 

 calculation; fout calculation of 

 so methodical a kind that a 

 machine ought to be found to 

 do it. The Tidal Harmonic 

 Analyser consists of an applica- 

 tion of Professor James Thom- 

 son's disk-globe-and-cylinder in- 

 tegrator to the evaluation of the 

 integrals required for the har- 

 monic analysis. The principle 

 of the machine and the essential 

 details are fully described and 

 explained in papers communi- 

 cated by Professor James Thom- 

 son and the author to the Royal 

 Society, in 1876 and 1878, and 

 published in the Proceedings for 

 those years; 8 also reprinted, with 

 a postscript dated April, 1879, in 

 Thomson and Tait's Natural 

 Philosophy, Second Edition, Ap- 

 pendix B. It remains now to 

 describe and explain the actual 

 machine referred to in the last 

 of these communications, which 

 is the only tidal harmonic an- 

 alyser hitherto made. It may be 

 mentioned, however, in passing, 

 that a similar instrument, with 

 the simpler construction wanted 

 for the simpler harmonic analy- 

 sis of ordinary meteorological 

 phenomena, has been constructed 

 for the Meteorological Com- 



Vide vol. xxiv. p. 262, and vol. xxvii. 

 p. 371. 



