220 Wtsconsin Academy of Sciences, Arts and Letters. 



part of the influx at the surface. This strait is large enough to- 

 give freedom to tides and currents, its length from Cape Trafalgar 

 to Europa point, in Sprin, is 36 miles and its width from 15 to 24 

 miles, its depth is as much as 5,000 feet. The spring tides at 

 Lissa Island in the Adriatic are 2|- feet and at Tripoli, Syria, at 

 the extreme east end of .the Mediterranean, they have still a range 

 ot two feet. 



The ISTew American Cjcopedia speaking of the age of the tide, 

 says: "This delay, which even at the Cape of G-ood Hope 

 amounts to fourteen hours, is still the subject of investigation and 

 is probably mainly due to friction." 



li the co-tidal charts by Whewell and others were correct, then 

 the delay would be much greater than that here mentioned, these 

 charts give the origin of the tide in the Pactfic, thence they bring 

 the tide across the Pacific and Indian ocean and into the Atlantic 

 by way of the Cape of Good Hope. The fact is, that this tide is 

 created in the A.tlanti3 ocean exactly on time with moon's tran- 

 sit, so that there is no delay at this point, but from here the tide 

 is twelve hours in reaching the United States coast, 14 in reaching 

 Spain and 24 hours readhing Dover by way of the British 

 Channel. 



From the same source we have the following: 



"If the tides arrive at the same place by two different channels 

 and one of them is retarded behind the other by six hours, in 

 consequence of traveling a longer route or in shallow water, the 

 semidiurnal tides will be destroyed by an interference of the 

 waves, that is, by the high water of one being superimposed on 

 the low water of the other." 



This phenomenon is common, two waves unite and one is the 

 result, but, this does not prevent a recurrence after 12 lunar 

 hours, the semidiurnal phase is not affected whatever in any ease. 

 If the tide divides on, and passes around an island, the two parts 

 unite and reform the wave, or, if the tides meet in a long channel 

 the result is a commotion which stops both until drawn down by 

 the succeediog tide-!, or they may, as at the Isle of Wight, cross 

 each other both ways causing double high tides. In this case the 

 tide from the west enters the " Solent" at ten hours with a range 



