THE TIDES. 143 



coast of a slanting shore where there are long 

 ocean waves, we see the gradual sinkings and 

 risings produced by them, and say that it is a 

 wave we see, not a tide, till one comes which is ex- 

 ceptionally slow, and then we say " that is liker a 

 tide than a wave." The fact is, there is something 

 perfectly continuous in the species of motion called 

 wave, from the smallest ripple in a musical glass, 

 whose period may be a thousandth of a second 

 to a " lop of water " in the Solent, whose period is 

 one or two seconds, and thence on to the great 

 ocean wave with a period of from fifteen to twenty 

 seconds, where ends the phenomenon which we 

 commonly call waves (Fig. 18, p. 144), and not tides. 

 But any rise and fall which is manifestly of longer 

 period, or slower in its rise from lowest to highest, 

 than a wind wave, w r e are apt to call a tide ; and 

 some of the phenomena that are analysed for, and 

 worked out in this very tidal analysis that I am 

 going to explain, are in point of fact more 

 properly wind waves than true tides. 



Leaving these complicated questions, however, 

 I will make a short cut, and assuming the cause 



