CATALOGUE OF INSTITUTIONS— DISTRICT OF COLUMBIA 



173 



on the recent survey of Georges Bank, the 

 approaches to New York Harbor, and the ap- 

 proaches to Chesapeake Bay. 



In the subject of tides, three notable achieve- 

 ments may be mentioned. First is the design of 

 the construction of a direct-reading tide predictor 

 by means of which tide predictions are made more 

 expeditiously and more accurately than before. 

 Second, the development of methods for deter- 

 mining with precision tidal datum planes from 

 short series of observations. Third, the develop- 

 ment of the stationary-wave theory of the tide, 

 which permits a better understanding of the 

 various features of the tide found in the seven seas. 



Location: Washington, D. C. 



Organization to which attached: Bureau of Department 

 of Commerce. 



Purposes and scope of activities: The results of coastal 

 surveys are published, for the guidance of naviga- 

 tion and the protection of life and property at 

 sea, on about 750 different charts which constitute 

 the basic product of the Bureau. The greater 

 part of the information shown on the charts is 

 obtained by extensive hydrographic and topo- 

 graphic surveys and the accuracy and adequacy 

 of such surveys in any region are, therefore, an 

 index of the condition of the charts of that 

 region. 



There is also a considerable amount of informa- 

 tion required by mariners that can not be shown 

 conveniently on charts. This includes sailing 

 directions and data relative to port facilities, 

 weather conditions, radio service, and similar 

 subjects. To supply this information the Coast 

 and Geodetic Survey publishes 12 Pilot volumes 

 for the coasts under the jurisdiction of the 

 United States and 3 Inside Route Pilots for our 

 inland waterways. 



The geodetic work of the Bureau has for its 

 principal object the establishment of a great 

 number of points, distributed along our coasts 

 and throughout the interior, to provide a founda- 

 tion or framework for practically all charting and 

 mapping operations. These are divided into two 

 general classes — triangulation stations, the posi- 

 tions of which, with relation to each other and 

 on the surface of the earth, are determined; and 

 bench marks, the elevations of which are accu- 

 rately known. 



The bureau's tidal investigations serve two 

 purposes with respect to chart production; first, 

 they provide data for the establishment of the 



reference plane and for the reduction of all sound- 

 ings to that plane; second, they enable the bureau 

 to compile annual tables of predicted tides and 

 currents, by means of which the mariner can 

 time the movements of his ship to take advantage 

 of the tide or, by using the tables in conjunction 

 with his chart, can ascertain the actual depths 

 at any time. 



With the increase in size of ships and the grow- 

 ing importance of economy in their operation, 

 it has been necessary in late years for the bureau 

 to extend the scope of its current investigations 

 which are carried on in connection with tidal 

 observations. Outside the bureau the results 

 of these operations are of great value in harbor- 

 improvement work, sewage disposal, and similar 

 projects. 



The magnetic surveys of the Bureau are 

 carried on for the primary purpose of providing 

 the data relative to magnetic variation that are 

 shown on all charts and airway maps and are 

 essential to the accurate use of the magnetic 

 compass. The results are equally necessary for 

 land surveying and for many branches of scientific 

 research. 



The activities mentioned above are all essential 

 branches of chart and map production work, 

 however, the Bureau is engaged in two other 

 activities. One of these is airway mapping. In 

 addition to being directly in line with other 

 charting operations, the assignment of this 

 duty to the Bureau is simply a case of utilizing 

 trained personnel and a modern map-making 

 plant to turn out additional work with no great 

 increase in overhead expenses. 



The other activity is seismology, or earthquake 

 investigation. This was delegated to the bureau 

 for the reason that the work required is admirably 

 adapted, both in the field and office, for pro.secu- 

 tion in conjunction with magnetic surveys and, 

 hke airway mapping, can be carried on with only 

 a moderate increase in operating expenses. 



The Coast and Geodetic Survey helps other 

 institutions by collecting samples of marine 

 plankton and bottom sediments. 

 Equipment: The Survey owns and operates ten sea- 

 going vessels, four of which are employed on the 

 Atlantic and Gulf Coasts, six on the Pacific and 

 Alaskan Coasts, and one in the Philippine Islands. 

 The last is owned by the Philippine Government. 

 In addition, it operates a number of smaller motor 

 vessels and wire drag launches for work imme- 



