282 WAVES OF THE SEA 



(from 15 feet to 20 feet I estimated) ' and also in 

 position, but the amount of shifting was not great 

 perhaps one -half of the length of the mound 

 of water. This staggering and heaving conveys 

 the notion of efforts so great that some breakdown 

 must soon occur. And while I watched enthralled 

 the breathless heavings of the standing waves, a 

 surge came rushing upon the shore where I stood, 

 as if the river would suddenly rise and overwhelm 

 me. I drew back, realising that my post of 

 observation was unsafe. Acting on the ordinary 

 experience of rivers as flowing with practically 

 steady motion, I had not sufficiently allowed for 

 the amount of throbbing in the Niagara Rapids. 

 Of course, the rush of water which drove me back 

 was not the commencement of a continuous rise, 

 but merely the discharge of a wave, and the water 

 receded again with a somewhat more deliberate 

 motion, only to make way for another dashing 

 surge. The surge was timed by the covering and 

 exposure of a rock : 



Number of Times Rock Covered. 



First Second Third Fourth Fifth 



Minute. Minute. Minute. Minute. Minute. 



35445 

 Average period, 14*3 seconds. 



1 The late Mr. T. V. Welch, formerly Superintendent of the 

 New York State Reservation at Niagara, informed me that they 

 are estimated at 30 feet when at their highest. 



