HEIGHT OF WA VES, 75 



The highest wave observed by M. de Tessan, during 

 the voyage of the Venvs, measured about 24 I'eet 

 from its crest to the bottom of its cavity. The great- 

 est height admitted by Humboldt, and at a distance 

 from any coast, is 37 feet. As to the mass of water set 

 in motion, observations were made by M. Siau, in St. 

 Paul's Bay, Isle of Bourbon, which seem to show that 

 it does not exceed a thickness of 600 feet. But the 

 height of the wave is supposed to furnish a clue to the 

 depth of the agitation it causes. Weber concluded, 

 from his celebrated experiments, that every wave 

 propagates its motion to a depth of about 350 times 

 its own height. If so, a wave only 6 feet in height 

 would stir the North Sea to its lowest abysses, while 

 a wave 30 feet high would make itself felt to a depth 

 of 10,000 feet. However this may be, we know that 

 the movement becomes very feeble even at a sliglit 

 depth, and it must soon become altogether insensible, 

 even if it continues to extend itself, because Weber 

 himself has demonstrated that it decreases in geo- 

 metrical proportion according to the depth. 



So long as a wave extends its motion downwards 

 in a deep place, it produces no effect on the soil. 

 Let it, however, wash against a bank or a shore, and 

 it begins to play a part well worthy of observation. 

 Sometimes, in combination with local currents, it 

 produces very curious phenomena. For example. 



