4 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS I,IETEOROLOGY 



been by no means completed— no, not even to the tenth part— 

 yet more knowlcdgo has been gained concerning the depths and 

 bottom of the deep sea, than all the Avorld had before acquired m 

 all previous time. 



10. Its probable deptli.^The system of deep-sea soundings thus 

 inaugurated does not thus far authorize the conclusion that the 

 overage depth of ocean water is more than three or four miles 

 (§ 3) °nor have any reliable soundings yet been made in water 

 over five miles deep. 



11. Belaiion between its depth and the leaves of the sea.— In very 

 shallow pools, where the water is not more than a few inches 

 deep, the ripples or waves, as all of us, when children, have 

 observed, are small; their motion, also, is slow. But when the 

 water is deep, the waves are larger and more rapid m their 

 procuress, thus indicating the existence of a numerical relation 

 between their breadth, height, and velocity, and the depth of the 

 water. It may be inferred, therefore, that if we knew the size 

 and velocity of certain waves, we could compute the depth of the 



ocean. 



12. Airifs imve tables.— Such a computation has been made, and 

 we have the authority of Mr. Airy,* the Astronomer Eoyal, that 

 waves of given breadths will travel in water of certain depths 

 with the velocities as per table : 



13. Hie earthqmlie of Simoda. — Accident has afforded us an 

 opportunity of giving a quasi practical application to Mr. Airy's 

 formuhe. On the 23rd of December, 1854, at 9.45 A.M.,t the 



* Encyclop. Metropol. , 



t Notes of a ratssian Officer, p. 97, No. 2 (Feb. 1856), vol. xxv., ^autlcal 

 Magazine, liOndon. 



