HYDROGRAPHY. ._: 185 



In the Gulf of Mexico, in addition to the deep-sea work 

 performed by Lieut.-Comraander Sigsbee, surveys have been 

 prosecuted on the west coast of Florida, near Cedar Keys, 

 and between St. Andrews and Pensacola, on the coast of 

 Louisiana and in the Mississippi River. At the mouths of the 

 Mississippi observations for currents, volume of discharge, 

 changes of depth, etc., have been continued. 



On the Pacific coast work lias progressed rapidly on the 

 coasts of California, Oregon, and "Washington Territory. 



Off-shore tidal-current observations have been continued, 

 and ten tide gauges on shore have been constantly observed 

 and recorded, in addition to those operated by hydrograph- 

 ic parties. 



The work of compiling the Coast Pilot for the Atlantic 

 coast and for the coast of Alaska has made steady progress, 

 while a large force in the office has been constantly employ- 

 ed in constructing charts from new surveys, and in the end- 

 less work of correcting older chart-plates in accordance with 

 recently discovered changes. 



An excellent precis of the work done by English Admiral- 

 ty Surveyors is given in the Nautical Magazine for July, 

 1877. 



The constant demand for more exact information regard- 

 ing very many partially surveyed regions, in order to devel- 

 op new channels of commerce, is very great and is constantly 

 increasing, and the world is indebted to English surveyors 

 for an immense amount of valuable work in this direction. 



Owing to the sandy nature of the bottom at the mouths 

 of several of the rivers and estuaries on the shores of Great 

 Britain, it is necessary at frequent intervals to re-survey them. 



In Yarmouth harbor, at the mouth of the river Thames, 

 in the Solway Firth, at the mouth of the river Tay, and 

 at the mouth of the river Shannon, marked changes were 

 found during the past year to have taken place in the chan- 

 nels and shoals. 



In the Mediterranean, Captain Wharton, P.N., in H.M.S. 

 Fawn, has continued the examination of the mouth of the 

 Nile and the entrance to the Suez Canal. 



A considerable advance of the land is shown to have taken 

 place at the Damietta mouth of the Nile, as compared with 

 its condition in 1856. A careful examination of the depths 



