CHAPTER III. 



TIDES. 



Theory of tides Spring tides Neap tides Tidal wave never perfectly formed 

 Priming and lagging of tides Effect of variations in distance of sun and moon, 

 also of declination Diurnal and semi-diurnal tides Equinoctial spring tides 

 Summer and winter tides Progress of the tidal wave Tidal range in Bay of 

 Fundy, Bristol Channel, etc. Tidal range in open ocean Tides in Mediter- 

 ranean Sea Double tides Tides at Batsham Tidal " establishment "Tidal 

 harmonic analyzer Mechanical prediction of tides Harmonic analysis of tidal 

 records Effect of wind upon tides Effect of atmospheric pressure upon tides 

 Effect of tidal range upon sea-works Use of, and facilities afforded by, 

 tidal range" Bore." 



ALMOST all works constructed in tidal seas are, in a greater or 

 less degree, affected by the tides. The subject is, therefore, one 

 which demands careful attention. 



Newton, Laplace, Airy, and others, have done much to explain 

 the observed phenomena of tides; but the difficulties which it 

 is needless to detail here connected with a complete explanation 

 of the subject are such that the conclusions or at least some 

 of them which have been arrived at, are admitted to be more 

 or less unsatisfactory, they having been based upon premises 

 involving arbitrary conditions which do not exist in nature, but 

 which it was, nevertheless, necessary to adopt, in order to bring 

 the subject within manageable limits. 



It is generally admitted that the admirable treatise by the 

 late Astronomer Royal, Sir G. B. Airy, published in the " Encyclo- 

 paedia Metropolitana," contains the most complete information on 

 the subject of tides of any work extant; and the deductions 

 drawn by him, from an examination of the several theories 

 which have been propounded, and also from experiments which 

 were conducted by Scott Russell, the Webers, and others, may 

 be considered sufficiently accurate for all practical purposes. 



In the present volume, a much more general description of 

 the subject than is there given must suffice. I have, however, 



