222 Wisconsin Acadimy of Sciences, Arts and Letters. 



remarks and it appears that in every instance the authors had a 

 very indifferent knowledge of tidal phenomena. 



Keel us was not far from correct when he said: " Cotidals ac- 

 cording Whewell are accepted, but it is not certain that things 

 occur in this way, in fact, it is asceitained that in each oceanic 

 basin the tide seems to start from the centre and be propagated in 

 all directions parallel to the general direction of the coasts." 



This remark was a welcome discovery wh«n the accompanying 

 chart began to develop into its present form, so also a statement 

 from an unknown author, that the tide possibly had its origin in 

 the middle of the India)i Ov3ean : also the report of a British 

 naval commander who stated ''that instead of a constant current 

 westward around the Cape of Good Hope he had known vessels 

 to remain stationary for days and even to drift to the east." Now 

 it is safe to say that had the tide been constantly in one direction 

 around the cape, as it was supposed to be, then the current would 

 also have been constant in the same direction. 



The tides of the British Channel and North Sea have already 

 been mentioned but owing to so singular phenomena a special in- 

 vestigation will be interesting. The accompanj^ing chart shows 

 every feature of these remarkable tides. 



The cotidal lines represent the progress at each hour of absolute 

 time; the age of the tide is reckoned from its origin in the South 

 Atlantic when the moon transits the meridian of Grreenwich at 12 

 o'clock noon or .midnight (this is at full and change). 



A tongue of deep water, over 2,500 fathoms deep, extends far 

 into the Bay of Biscay, and when the tide arrives of! this point 

 it makes a decided lateral move into the bay with great velocity, 

 from the llth to the loih hour, at the same time approaching the 

 shores of Ireland and England, dividing on Cape Clear at the 

 16th and Lands End a little before the 17th hour; the southeast 

 portion pas:?es through the British channel and Dover straits in a 

 northeast direction at the 2-lth hour, and it here passes a tide on 

 its west 12 hours older. Meeting as they do, these tides reflect 

 and preserve their individuality on opposite shores in opposite 

 directions. The tide from the channel keeps along the east shore 

 and meets a tide .off the coast of Jutland 12 hours younger than 



