Annual Report on the U. 8. Coast Survey. 317 
dred and eighty fathoms, divides itself into two principal branches, 
separated by a portion of cold water, and that the transition from 
the cold water, along and next to the coast is almost instantane- 
ous, as if the two were separated by a nearly perpendicular wall, 
slightly inclining to the east at the top. he plan of operation, 
commenced by Lieut. Bache, has been continued during the past 
year, and a series of observations on the temperature at different 
depths has been made across the stream off the coast of Virginia, 
North and South Carolina, Georgia and Florida, for the purpose 
of comparison with those made the year before across the same 
places and to ascertain what changes may have taken place. 'The 
results are highly interesting, the same general phenomena are 
presented as in the former survey, two principal divisions of the 
stream are observed, but these show a tendency in the last survey 
to separate into others, the points of maximum temperature are 
not in the same places and the mean or average temperature is 
different. The investigation becomes more interesting as it is 
ther pursued, and we doubt not the superintendent, with his 
love for physical science, will not fail to direct such observations 
as may lead to a more definite knowledge than we now possess 
of this interesting phenomenon of the ocean. 
Changes in Channels and Shoals, §c.—One object of the 
Coast survey is to ascertain the character and direction of the 
changes which may be going on in difterent parts of the coast, to 
Provide the means of observing them in future, and to furnish 
the data on which the plans of controlling them may be founded. 
ing the past year the changes in the Delaware River near the 
Pea Patch have been examined, and were found to consist in the 
closing of the old eastern channel by the extension of the Bulk- 
shoal to meet the spit, extending from the upper part of the 
Pea Patch island. he same time, the new eastern channel 
has widened and deepened. ‘These changes have been accurately 
marked on the map of the coast survey, which will thus furnish 
the means of discovering any future alteration. In this way the 
Tecords of the coast survey will afford the data for solving prob- 
‘ems of a most interesting character, as for example, the rate of 
merease of the delta of the Mississippi. al 
__ tidal Observations.—A series of observations on the variation 
of the height of water and the currents produced by the tides 
ave been established at different points along the coast. The 
observations made at Old Point Comfort have been discussed 
by Lieut, Com. Davis, U.S.N., under the immediate direction of 
the Superintendent, for the purpose of ascertaining the effect of 
the Variations in the moon’s parallax and declination. In elimi- 
Changes appear as residual errors. The effect of change of pres- 
Sure and of wind on the height of water is already apparent, and 
