116 LECTURES. 



throiigli the weft of America history, through all the great political 

 transactions as well as the arrangement of private affairs, wherein it 

 becomes ramified into innumerable branches. And still this country 

 has never yet thought even of establishing an institution to supply 

 every branch of the government with a kind of information the want 

 of which is so continually felt. It is to be hoped, however, that in 

 this respect America will yet point the way to the older nations of the 

 world. 



VII. USE OP FORMER MAPS IN DIFFERENT PRACTICAL QUESTIONS. 



Although in its principal features the configuration of the surface 

 of our globe remains unaltered, still there are continually going on. 

 in every part of it, changes which appear insignificant in comparison 

 with the great mass of our continents and oceans, but which are some- 

 times of the utmost importance for the pigmy works of man and for 

 the enterprise and existence of nations. 



Our mountains are constantly being lessened in height, our rocks 

 crumble down from year to year, never to be built up again. Some- 

 times a volcano or a new island rises from the depths of that fiery 

 abyss which is concealed under our waters and blooming lands. Our 

 rivers are continually changing a little the direction of their courses. 

 They abrade their banks on one side, and break through with new 

 branches, whilst the opposite side is left dry and allowed to increase. 

 They gradually float away old islands, or form new ones which did 

 not exist before. The changes are particularly great at the mouths 

 of the rivers and in their deltas near the sea-shore, where the current 

 encounters the influence of the motions of the sea and its strong winrls. 

 There one arm of a river is choked with sand, and in time entirely 

 disappears, whilst another gradually deepens, and from a little creek 

 is transformed into a broad and navigable channel. 



On the shores of the ocean itself the changes are upon a larger scale. 

 The sea has swallowed whole tracts of country, and has produced new 

 ones from its depths. In the course of centuries, banks of sand are 

 formed, or shift their place. Many capes and peninsulas are continu- 

 ally melting away under the action o: the waves ; others grow larger 

 under the influence of the meeting of contrary currents ; whilst others, 

 again, seem only to vary their position, and, like enormous pendulums 

 thrown out into the waters, show a tendency to increase for a certain 

 period on one side, and then for a like period on the other. 



It is even believed that the very foundations of the gigantic crust 

 of our globe are not quite settled yet, and that some parts of our coasts 

 are constantly heaved up from beneath, whilst others by a sIoav pro- 

 cess are sinking ; whence it results tliat they are perpetually varying 

 the outlines which they form with the unchanging level of the ocean. 



An accurate knowledge of these changes and their tendencies is not 

 only very interesting for the history of the past and for general science, 

 but is also of the greatest consequence for the future and for practical 

 purposes. 



Some of the processes by which those changes are effected are 

 rapid in their action, and can be observed and recollected by indi- 



