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 in 
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. 
