THE REV. W. WHEWELL'S RESULTS OP TIDE OBSERVATIONS. 87 



rents of the water. But this supposition is altogether gratuitous. The place of the meet- 

 ing of the two tide-waves, which come in opposite directions, is the part of the coast 

 where the tide is later than it is on either side of that part. For example, we know 

 that on the coast of Dorsetshire and Hampshire the tide-hours are VII. VIII. IX. 

 going eastward, and that on the coast of Norfolk the tide-hours are VII. VIII. IX. 

 proceeding southwards. The tide-waves, therefore, move in an opposite direction 

 along these coasts, and must meet at some intermediate point, as, for instance, on the 

 coast of Kent ; and at this point the tide is later than it is if we go along the coast 

 either to the east and north, or to the south and west. But these motions of the tide- 

 waves must be distinguished from the motions of the streams which bring the tide, as 

 will be obvious when it is recollected that the tide-wave travels from the Land's End 

 to the Isle of Wight in six hours. At the place where the tides meet there will not 

 necessarily be anything more marked in the stream of flood and ebb than at any 

 other point. The tendencies to opposite tide-streams may partially balance each other 

 during a part of the flow and of the ebb, and leave only the diff'erence of tendency in 

 actual operation. There may be strong and conflicting tide-streams produced under 

 certain circumstances ; but these results will depend much more upon the local con- 

 ditions of the ground than upon the general course of the tide-wave. 



The meeting of the tides, however, will not be a single point ; for by the laws of 

 fluids the two opposite undulations, which we term the tide-waves, will be propagated 

 independently of each other, and the fluid will be affected by both. If they were thus 

 propagated without any loss of magnitude, we could easily trace the consequences. 

 Let the tide-wave on the south coast move eastward so as to bring high water to cer- 

 tain places, 



A. B. C. D. E. F. G. H. K. L. M., 

 at the hours 



VI. VII. VIII. IX. X. XI. XII. I. II. III. IV., 



and let the tide coming from the north and east in the opposite direction arrive at the 

 same places at the hours 



IV. III. II. I. XII. XI. X. IX. VIII. VII. VI. 



It is then manifest that the tide at F. will still take place at XI. ; also the tides at 

 E. and D. will occur about XL, the hour intermediate between X. and XII., and be- 

 tween IX. and I. In the same way the tide at G. and H. will be about XL I do not 

 say exactly dit XL, because each tide may diminish in amount as it advances ; and for 

 this reason each tide may, at a certain distance after their meeting, less affect the 

 other. From these considerations we may expect the tide-hours along such a coast 

 to be as follows ; 



The question now remains to be answered. Do we find any such succession of 

 tide-hours as this on the coast of Britain ? And to this the coast-guard observations 



