On the Progress of the Tidal Wave of the Hudson River 17 
directly and indirectly. The inner current is the one by which 
the flood and ebb tides draw, by the lateral communication of. 
motion, the water from Sandy Hook bay, and the outer is simi- 
larly related to those tides as they pass False Hook channel. The 
velocities and directions which have been found, prove this con- 
clusively. An important observation for navigation results from 
this, for more than seven hours out of the twelve there is a north- 
wardly current running through False Hook channel, which assists 
vessels entering New York harbor on the ebb tide, and is to be 
avoided in passing out with the ebb. This northwardly current 
runs on the inside for eleven hours out of the twelve. It is the 
conflict of these two northwardly currents outside and inside, 
and the deposit of the materials which they carry to the point of 
the Hook, which causes its growth. ithin a century, it has 
increased a mile and a quarter, and at about the rate of one- 
sixteenth of a mile a year, on the average, for the last twelve 
years. Flynn’s knoll, on the north side of the main ship channel, 
does not give way as the point of the Hook advances. The im- 
portance of watching this movement cannot, therefore, be over- 
Stated. The mode of controlling the growth is obvious from the 
results obtained. The observations are still continued to obtain 
the necessary numerical results. 
the Commissioners on Harbor Encroachments ; by A. D. Bacug, 
Supt. U.S. Coast Survey.—(A bstract.) 
Provements projected for the Hudson river at the Overslaugh, 
and indeed in the whole distance from Troy to. New Baltimore. 
Nine tidal stations were in the course of occupation between Gov- 
€rnor’s Island, New York, and Greenbush, opposite Albany. At 
the two terminal stations Saxton’s self-registering guages were 
