192 CORALS AND CORAL LSLANDS. 



tion from two hundred and sixty-seven experiments, extending 

 over twenty-three successive months, that the average force for 

 Skerryvore, for five of the summer months, during the years 

 1843, 1^44? was six hundred and eleven pounds per square 

 foot ; and for six of the winter months of the same years it 

 was two thousand and eighty- six pounds per square foot, or 

 three times as great as during the summer months. During 

 a westerly gale, at the same place, in March, 1845, ^ pressure 

 of six thousand and eighty-three pounds was registered by 

 Mr. Stevenson's dynamometer (the name of the instrument 

 used). He mentions several remarkable instances of trans- 

 ported blocks. One of gneiss, containing five hundred and 

 four cubic feet, was carried by the waves five feet from the 

 place where it lay, and there became wedged so as no longer 

 to be m.oved. Of the manner in which it was moved, Mr, 

 Reid (as cited by Mr. Stevenson) says : " The 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-Hne above it, 

 making a perpendicular rise of from thirty-nine to forty feet 

 above high-water level. On the incoming waves striking the 

 stone, we could see this monstrous mass, of upwards of forty 

 tons weight, lean landward, and the back-run would uplift it 

 again vi^ith a jerk, leaving it with very little water about it, when 

 the next incoming wave made it recline again." 



Mr. Stevenson states also that the Bell Rock Lighthouse, 

 in the German Ocean, though one hundred and twelve feet in 

 height, is literally buried in foam and spray to the very top 

 during ground swells, when there is no wind. On the 20th 

 of November, 1827, the spray rose to the height of one hun- 

 dred and seventeen feet above the foundations or low-water 

 mark ; and deducting eleven feet for the tide that day, it 

 leaves one hundred and six feet, which is equivalent to a 

 pressure of nearly three ions per sqtiarefoot. 



With such facts, any incredulity respecting the power of 

 waves should be laid aside. Moreover, it may be remarked 

 that the Pacific is a mucli wider ocean than the Atlantic, with 

 far heavier waves in its ordinary state. 



