On Coral Reefs and Islands. 331 



But on land, there is the decay of the year and that of old age 

 producing vegetable debris; and storms prostrate forests. And 

 are there corresponding ettects among the groves of the sea? 

 It has been shown that coral plantations, from which reek pro- 



ceed, do not grow in the ''calm and still" depths of the ocean. 



They are to be found amid the very waves, and extend but little 

 below a hundred feet, which is far within the reach of the sea's 

 heavier commotions.^ Here is an agent which is not without 

 Its effects. The enormous masses of uptorn rock found on many 

 of the islands may give some idea of the force of the lifting 

 wave; and there are examples on record, to be ?oundi in various 

 Treatises on Geology, of still more surprising effects.f 



^ During the more violent gales, the bottom of the sea is said, by different au- 

 thors, to he disturbed to a depth of three hundred, three hundred and fifty, or even 

 five hundred feet, and De la Ileche remarks, that when the depth is fifteen fathoms, 

 the water is very evidently discolored by the action of the waves on the sand and 

 mud of the bottom. In the Comptes RcitdnH, t. xii, ^74, M. Sian mentions tluit par- 

 allel ridges are ft)rmed on the bottom, by the motion of the water, wliich may be 

 readily distinguislied at a depth of at least t^vcnty meters. The hollows between 

 such ridges or zones are occupied by the heavier substances of the bottom. Similur 

 zones were di>;tinguis]ied at a depth of one hundred and eighty-eight meters, to the 

 Northwest of the St. Taul's Eoads. 



. t Lyell, vol. ii, p. 88-40. Speaking of the force of waves on coasts, Lyell men- 

 tions the transportation of a block of stone, ninety feet from its bed, which was 

 eight feet two niches, by seven feet, and five feet one inch in its dimensions, and 

 another nine feet two inches, by six and a half feet, by four feet, having been *' hur- 

 ried up an acclivity to a distiUice of one hundred and fifty feet." 



In an article on the subject, by Thomas Stevenson, of Edinbnigh, published m 

 the Transactions of the Royal Society of Edinburgh, (vol. xvi, 1845,) it is stated, as a 

 deduction from two hmithed and sixty-seven ex]>erinients, extending over twenty- 

 three successive months, that the averai^e force for Skerryvore, for five of the sum- 

 nier months, during the years 1S43, 1844, was six hundred and eleven pomids per 

 square foot ; and for six of the winter months of the same year, it was two thou- 

 sand and eighty-six pounds per square foot, or three tinges as great as during the 

 summer months. During a westerly gale, at the same place, in Mardi, 1845, a pres- 

 sure of six thousand and eii<hty-tlu-ee pomuls was registered by Mr. Stevenson's dy- 

 pamometer, (the name of the instrument used.) He mentions several remarkable 

 instances of transported blocks. One of gneiss, containing five hundred and four 

 cubic feet, was carried by the waves five feet from the place wliere it hiy, and there 

 became wedged so as no longer to the moved. Of the manner in which it was 

 inoved. Mr. Reid (as cited by Mr. Stevenson) says: "Tlie sea, when I saw it striking 

 the stone, would wholly immerse or bury it out of sight, and the run extended up 

 to the grass line above it, makiiig a perix-ndicular rise of from thirty-nine to forty 

 leet above high water level On the mcoming "R-aves striking the stone, we could 



Mr. Stevenson stages also that the Bell Rock Lighthouse i a the German Ocean, 

 tcough one hundred and twelve feet in height, is literally buried in foam and spray, 

 to the very top, (Uu'ing around swells, when there is no wind. On XhQ 20th of Tio- 

 jember, 1827, the spray^rose to the height of one hundred and seventeen feet above 

 ^he foundations or low water mark; and deducting eleven feet for the tide tliat 

 ^y> It leaves one himdred and six feet, which is equivalent to a pr ure of nearly 



^f^ree torn per sqtiare foot ^ v ni i-i 



With such facts, any incredulity respecting the power of waves should \Hi hud 

 a^ule. Moreover, it may be remarked that the Pacific is a much wider ocean than 

 the Atlantic, with far heavier waves in its ordinary state. 



