226 Wisconsin Academy of Sciences^ Arts, and Letters. 



experiment and the various phases aud interferences may be pro- 

 duced just as they occur in nature. 



If we take a basin of water and agitate the same, we may pro- 

 duce one or more waves ; if now we regulate the impulse while 

 we observe the motion, we may time the same so as to produce 

 regular oscillations which will continue until a change of force 

 takes place; whenever such change takes place either in amount 

 or duration, interferences will appear which after a time will cause 

 the wave or waves to come to a state of rest, but if the same im- 

 pulse continues, the oscillations begin again, increase to maximum, 

 diminish and again cease. 



This will be the case whether the impulse be greater or less or 

 the time faster or slower than that necessary to produce regularity. 

 This is practically true of the great lakes, the oscillations observed 

 are the effect of the tide producing force which is entirely dispro- 

 portioned to the extent of the volume acted upon, the resulting 

 irregularities recur in periods from which the tide may be deter- 

 mined by elimination. 



There are many peculiarities attending the tides as they meet 

 with the varied obstructions of the coast, prominent among these 

 is that the range of tide is less at the most advanced portions of 

 a continent than at either side. The advancing tide in these cases 

 meets with the resistance of the submerged portion of the Cjpe 

 long before reaching the coast and departs to either hand, thereby 

 diminishing the tide at the cape, which, having reached the coast, 

 divides, and by its momentum crowds upon that part of the tide 

 already making in the bays or indentations of the coast on either 

 side. 



We have thus far followed the tidal phenomena through all 

 their principal phases with the moon as the cause or Companion of 

 the same. 



In order to deduce the cause of the tides we will refer to first 

 principles and then compare facts with the laws of nature. Ac- 

 cording to Keppler's ^ two first laws, based upon the observations 



'Johan Keppler, Wurtemburg. Born 1570, died 1630. 1st and 2d, 1609; 

 3rd, 1618, May 15. 



