PRELIMINARY REMARKS. 
13 
the general coast line. The inclination of the Eocenic plain 
is equal to one foot per mile. It extends inward to Raleigh, 
which is two hundred feet above the sea level. Upon the 
Atlantic coast we learn the nature of the action of water mov¬ 
ing in wave masses. The slope of the beach is gentle to the 
surf line5 here the bank steepens, and the crested wave rotates 
vertically upon itself, giving origin to the ground wave or 
undertow, while a portion shoots forward in thin sheets, rip¬ 
pling the sands over which it flows. Upon the Carolina coast 
this action is mainly constructive.' 
§11. The constructive action of water is equally manifest in 
the formation of shoals. The tide-wave, which travels north¬ 
east, transports detritus, which is deposited at any point where 
an obstruction lies in its way. A portion of a wreck is suffi¬ 
cient to form a shoal. 
§ 12. It has been said already that the bottoms of oceans and 
seas are not spread out in level plains. They have all the 
diversities of dry land, rising in some places into mountains 
and hills; in others, sinking into deep valleys. It is in these 
deep valleys that sounding lines fail to reach the bottom. 
Extensive and comparatively level banks exist, where the water 
has only a moderate depth. The Atlantic’s shore is skirted by 
extended ridges, which are formed or moulded by the joint 
action of tides and waves. 
§ 13. Animals live upon the ocean’s bottom; but different 
kinds inhabit it at different depths. They are rarely found liv¬ 
ing below the depth of 180 feet. Vegetables grow in the 
ocean. They can subsist at the depth of 300 feet. The most 
favorable positions for animals and plants are near the shore, 
where the water is comparatively shallow. In deep water they 
select the slopes of ridges. The summits are generally avoided 
on account of the disturbance by waves. Great pressure, and 
the absence of light in deep water, are unfavorable to life; and 
the more profound abyses, like the heights of the Himalaya 
and Andes, are dreary wastes—the one from its darkness and 
pressure of the superincumbent water, the other from its exces- 
