PRELIMINARY REMARKS. 
19 
own coast flows northward, and carries its burthen onward; 
and at every opening mouth of a river it receives accessions, 
which, as a common carrier, it bears along, or gives it a new 
distribution. The conjoint actions of waves and tides are not 
only to carry, but break down, the bars and ridges which they 
have formed across inlets and bays. Bays and inlets may have 
been shut off from the ocean for centuries, or until their waters 
become fresh, and peopled with fresh water tenants, both from 
the animal and vegetable kingdoms. Again a high tide, 
accompanied with high waves and. winds, breaks down the 
bar, when it is at once filled wdth salt water. The animals 
and vegetables of fresh water die, and are replaced by the 
marine. Such alternations are well established facts. These 
views are illustrated by the changes in Albemarle and other 
sounds upon our southern coast. 
Water moving in masses, as in ocean rivers, modifies the 
present surface of the earth. These great rivers are only car¬ 
riers; they take what is committed to them, but they do not 
furnish the matter they carry. The Gulf stream is an ocean 
river. The great terrestrial rivers, as the Amazon, La Plata, 
Orinoco, Mississippi, Ganges, and Brahmapootra, are the con¬ 
tributors to the ocean rivers. The density of sea water aids in 
the wider distribution of matter committed to it. The great 
river, called the Gulf stream, originates in the Atlantic. 
Beginning near cape Horn, it is there divided: its main cur¬ 
rent flows down the western coast of America, but it turns sud¬ 
denly to the west, and is lost in the great equatorial current of 
the Pacific; it then crosses the ocean in the parallels of 26 and 
24 N. It is 350 miles broad when it impinges upon the coast 
of China, the eastern peninsula, and islands of the Indian archi¬ 
pelago, where it is again divided. A portion is deflected to 
join the great equatorial current of the Indian ocean, when it is 
impelled by the south-east trade wind: it however maintains a 
westerly course between 10° and 20° parallels of south latitude. 
It is divided a third time by the island of Madagascar. One 
part bends round its northern end, and flows through the 
