12 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOKOLOGY. 



carry off only the water -which is superfluous, and would be 

 pernicious. They remove it to other lands, where its agency is 

 required, or treasure it up, as the material of clouds and dew, in 

 the crystal vault of the firmament, the soiu:ce, when the fitting sea- 

 son comes round again, of those deluges of rain which provide for 

 tiie wants of the year. Such are some of the examples which may 

 be supplied of general laws operating over nearly the whole siu'face 

 of the terraqueous globe. Among the local provisions ancillary to 

 these are the monsoons of India, and the land and sea breezes 

 prevalent throughout the tropical coasts. 



36. "We have not noticed the tides, which, obedient to the sun 

 Tiie tides. and moon, daily convey two vast masses of water 



round the glebe, and which twice a month, rising to an miusual 

 height, visit elevations which otherwise are diy. Dming one 

 half of the year the highest tides visit us by day, the other half 

 by night ; and at Bombay, at spring tide, the depths of the tvro 

 differ by two or three feet irom each other. The tides simply 

 rise and fall, in the open ocean, to an elevation of two or three 

 leet in all; along our shores, and up gulfs and estuaries, they 

 sweep with the violence of a torrent, having a general range of ten 

 or twelve feet — sometimes, as at Fundy, in America, at Brest and 

 Mihord Haven, in Europe, to a height of from forty to sixty feet. 

 The tides sweep our shores from filth, and pm'ify our rivers and 

 inlets, affording to the residents of om- islands and continents the 

 benefits of a bi-dimiial ablution, and giving a health, and freshness, 

 and pmity Avherever they appear. Obedient to the influence of 

 bodies many miUions of miles removed from them, their subjection 

 is not the less complete ; the vast volume of water, capable of 

 crushing by its weight the most stupendous barriers that can be 

 opposed to it, and bearing on its bosom the navies of the world, 

 impetuously rushing against our shores, gently stops at a given 

 line, and flov^^s back again to its place when the word goes forth, 

 ' TIius far shalt thou go, and no farther ;' and that which no human 

 povrer or contrivance could have repelled, returns at its appointed 

 time so regularly and sm^ely that the hour of its approach, and 

 measure of its mass, may be j)redicted vfith unerring certainty cen- 

 tmies beforehand. 



37. " The hurricanes which whirl vdth. such fearful violence 

 Hurricanes. ovor the surfaco, raising the waters of the sea to 



enormous elevations, and submerging coasts and islands, attended 

 as they are by the fearful attributes of thunder and deluges of 



