118 SOUTHERN AND CENTRAL PROVINCES. [Part VII. 



tion, of advance aucl retrogression, must be presumed 

 until the earth's attraction and the effects of friction shall 

 have quite checked the movement.^ Thus the periods 

 within which the principal tide-waves succeed one another, 

 and the oscillations to which they give rise, originate de- 

 rivative tide-waves of form and character so pecuhar as 

 to call for a more attentive mvestiojation than has hitherto 

 been devoted to them.^ 



It must not, however, be forgotten, that the tidal 

 phenomena which affect the Hmited zones of waters, on 

 either side of the Indian peninsula (waters, which, if 

 left to themselves, would have a tendency, when un- 

 affected by the attraction of the moon, to be restored 

 to a condition of normal equilibrium), receive still 

 further comphcation from the marginal efflux of the 

 tide-wave of the great Indian Ocean. This tide-wave 

 itself is not free, but modified in its turn by impingement 

 against the African continent, and by the deportment 

 of that continuous swell, " immensely broad and exces- 

 sively flat,"^ which sweeps comparatively unchecked 

 round the world between the parallels of 40° and 60° 

 south. In our present limited knowledge of facts, we are 

 not in a position to determine what changes of level or of 

 " stream " (not necessarily co-existent phenomena) may 

 result from these various sources of distm-bance. 



In the harbour of Galle, the daily period of high-Avater 

 is so materially modified by the phase of the monsoon, 

 and the strength and direction of the currents, as weU as 

 of the off and on shore ^vinds, that the very moderate 

 ascent and depression of level (somewhat less than two 

 feet) produced by luni-solar influences, have Iiitherto 

 attracted but httle attention from any except the more 

 scientific seamen, who may liave made sustained observa- 

 tions in order to eliminate these accidental variations 



^ A'ide Appendix to the Voyoge of I "^ Babbage, Ninth Bridgcwatei' 

 the Beayle,\o\,\\. ])s '177. 7/-eof/'w, Appendix, p. 218. 



I 2 IIekschel, Outlines, ^-c, p. 497. 



