8 TIDAL EVOLUTION. 



the Caspian, the Baltic aad other confined areas; their enor- 

 mous heights, on the other hand, in such places as the English 

 channel and the Bay of Fundy. The high tides of both of the 

 latter places are especiallyinteresting to me, having witnessed 

 them personally from the end of the three-mile pier at Havre 

 on the Channel, and from the wharfs at St. John, N. B., on 

 the Bay of Fundy. Time, however, will not permit of this, 

 and I pass on at once to the consideration of the dynamical 

 question of the friction which the tides are causing on the 

 earth and its effect upon the diurnal motion of the planet. 



No truth rests on more firm foundation than the axiom 

 that work cannot be accomplished without the consumption 

 ot energy in some of its forms. This is based upon the immu- 

 table law of correlation of forces. 



Now the tides are performing a w r onderful amount of work, 

 rebuilding our continents, hollowing out bays and aiding in 

 the formation of bars, besides raising bodily at the present 

 time, all the waters of the earth on an average three feet every 

 24 hours. In past ages the force displayed was much greater, 

 depending of course upon the proximity of the moon. Thus, 

 as we shall see a little later, when the moon was only 40,000, 

 instead of as at present 240,000, miles from the earth, the 

 tides, in place of averaging three feet, did indeed average 648 

 feet in height. Such tides as these would sweep almost every 

 city from the face of the earth. Just reflect upon what an 

 enormous amount of w r ork tides like these must have been able to 

 accomplish, and what important factors they must have been 

 in the evolution of the early stages of the earths' crust. 



But from what source is the energy derived at the expense 

 of which all this work was and is today performed? 



As the moon is the direct cause of the tides, it would, at 

 a superficial glance appear that we might be justified in at- 

 tributing the source of energy to our satellite. But is this 

 true? Will it hold good? No doubt it seems plausable, but 

 it is, nevertheless, a fallacy. To illustrate this, permit me to 

 quote an illustration from Sir Robert Ball. He says that it 

 is one of those cases by no means infrequent in dynamics, 

 where the truth is widely different from what seems to be the 



