DEPTH ~OF THE OCEAN. 9 



miles, were, examined by Ehrenberg, who found 135 different forms 

 of Infusoria represented, and among them twenty-two species new to 

 him. These Protozoa draw from the sea the mineral matter with 

 which it is charged that is, the lime or the silica, which form their 

 shell. These shells accumulate after the death of the animal, and 

 form the bottom of the ocean. The animals construct their habitations 

 near the surface ; when they die, they fall into the depths of the ocean, 

 where they accumulate in myriads, forming mountains and plains in 

 mid ocean. In this manner, we may remark en passant, many of 

 the existing continents probably had their birth in geological times'. 

 The horizontal beds of marine deposits, which are called sedimentary 

 rocks, and especially the cretaceous rocks and calcareous beds of the 

 Jurassic and Tertiary periods, all result from such remains.* 



The sea level is, in general, the same everywhere. It represents 

 the spherical form of our planet, and is the basis for calculating all 

 terrestrial heights ; but many gulfs and inland seas open on the east 

 are supposed to be exceptions to this rule : the accumulation of 

 waters, pressed into these receptacles by the general movement of 

 the sea from east to west, it is alleged, may pile up the waters, in 

 some cases to a greater height than the general level. 



It had long been admitted, on the faith of inexact observation, 

 that the level of the Red Sea was higher than that of the Mediter- 

 ranean. It has also been said that the level of the Pacific Ocean at 

 Panama is higher by about forty inches than the mean level of the 

 Atlantic at Chagres, and that, at the moment of high water, this 

 difference is increased to about thirteen feet, while at low it is over 

 six feet in the opposite direction. This has been proved, so far as 

 direct evidence goes, to be an error in so far as regards the difference 

 in level of the Red Sea and Mediterranean ; and the opening of the 

 Suez Canal has now furnished convincing proofs of it. Recent 

 soundings show that the mean level of the Pacific and Atlantic 

 Oceans are identical. 



It has been calculated that all the waters of the several seas 

 gathered together would form a sphere of fifty or sixty leagues m 

 diameter, and, supposing the surface of the globe perfectly level, 

 that these waters would submerge it to the depth of more than 600 

 feet Again, admitting the mean depth of the sea to be 13,000 feet, 

 its estimated contents ought to be nearly 2,250,000,000 of cubic 

 miles of water ; and, if the sea could be imagined to be dried up, all 



# * " World Before the Deluge," 2nd edition. 



B 



