34 WRITINGS OF JOSEPH HENRY. [1824- 



interesting phenomenon. It is not caused, as in the main 

 ocean, by the direct action of the sun and moon, but is pro- 

 duced by a vast wave, propelled by the force of the Atlantic 

 tide, along the slightly inclined plane of the bed of the river. 

 The crest of this wave passes through the whole distance of 

 151 miles, between New-York and Troy, in from seven to 

 nine hours. 



The comparative importance of the Hudson, as a great 

 commercial inlet to the western territory of the union, may 

 be inferred from the fact, that it is the only Atlantic river, 

 with the exception of the St. Lawrence, that has not its nav- 

 igation soon interrupted by a precipitate descent from the 

 mountain chain. At the Highlands the Hudson penetrates 

 the primitive rock, and admits the ocean tide one hundred 

 miles to the interior of the ridge, at whose foot, in every 

 other Atlantic river, it is stopped.* Its tributary, the Mo- 

 hawk, as we have seen, occupies the bottom of a depression 

 which deeply indents the remaining ridges of the Appala- 

 chian mountains, and thus connects by an easy pass the 

 valley of the Hudson with the basin of the St. Lawrence. 

 Nature has thus done more by the valleys of the Hudson 

 and the Mohawk, and that to the south of Lake Michigan, 

 towards uniting the waters of the Atlantic with those of the 

 Mississippi, than the utmost efforts of art can ever hope to 

 accomplish in any other part of the country. 



The importance of these peculiar topographical features 

 was duly appreciated by the projectors of our canal policy, 

 and the Erie and Champlain canal, with those in contem- 

 plation for uniting the former with the waters of the Susque- 

 hanna and Lake Ontario, fully develope the natural facilities 

 for internal navigation poss.'^ssed by this state. 



In a physical point of view, these works produce changes 

 which it could scarcely have been believed that the power 

 of man could have accomjDlished. The waters of the Tioga 

 river, which now entirely contribute to swell the volume of 

 the Susquehanna, by the construction of the artificial chan- 

 nel of the Chemung canal, will in part be conducted to 



* Gallatin's Keport. 



