FERTILITY OF THE SEA. 253 



not the least doubt that they were under the 

 waters, inasmuch as they contain shells, and skele- 

 tons, and entire fishes, which are adapted for 

 the deep water. 



The mean level of the sea may be taken as the 

 line of greatest fertility both in the water and on 

 land, and both in the animal and the vegetable 

 kingdoms, because it is the line of the greatest 

 action of both the sun and the air. It is probable 

 that the sea sinks down as much below that line 

 in proportion to the extent of its surface, as the 

 land rises above it ; and it is also probable that 

 the fertility of the sea diminishes as the depth in- 

 creases, just as that of the land does with increase 

 of height. But it is probable, nay, it is certain, 

 that the fertility of the sea cannot diminish so 

 rapidly as that of the land ; because, as we de- 

 scend there are pressure and condensation, which 

 are sources of sensible heat, while, as we ascend, 

 there are elasticity and expansion, which are 

 sources of sensible cold. Thus it is -neither im- 

 probable nor unphilosophical to suppose, that 

 though the inhabitants of the sea vary at different 

 depths, just as those of the land do at different 

 heights, yet that the sea may be well replenished 

 with its peculiar plants and animals at depths 

 measuring more than the height of the highest 

 mountain. Consequently, if we carry our imagi- 

 nation backward to the time when the uniform 

 solid spheroid was covered with the two miles of 

 water, we are upon legitimate ground when we 

 say that the surface of that spheroid under the 

 water may have been abundantly stocked with 

 plants and animals, and the water itself as abund- 

 antly as any part of the ocean is at present. 



