64 



The National Geographic Magazine 



work which becomes invaluable in time 

 of war. 



This was well exemplified during our 

 civil war, when the most successful 

 blockade-runners were commanded by 

 men, generally ex-naval officers, who 

 had been engaged in the Coast Survey 

 in the vicinity of their blockading op- 

 erations. If this was then true of our 

 own coast, how much more so will it be 

 of foreign coasts in the event of any 

 future war ! This fact was also evi- 

 denced during the late Spanish- Ameri- 

 can war. Nearly all of the many officers 

 who distinguished themselves during 

 that period, particularly those who oc- 

 cupied ranking positions, had seen good 

 surveying service either in the Navy or 

 in the Coast Survey. This I have 

 taken the liberty of demonstrating by 

 the exhibition of a few charts — one the 

 result of the work of Admiral Dewey, 

 one that of Admiral Charles E. Clark, 

 and one that of the late Admiral John 

 W. Philip. 



Lack of space only prevents exhib- 

 iting equally good work by many 

 other of our prominent officers, but I 

 cannot properly let the opportunity 

 pass without calling attention to some 

 of our many naval officers whose work 

 in hydrographic surveying will never 

 be forgotten : Commodore Wilkes on 

 the Grand Banks and in the Pacific and 

 Antarctic, Commodore Perry in the 

 waters of Japan, Commodore Rodgers 

 and Commanders Berry and Stockton 

 in the North Pacific and in Bering Sea, 

 Lieutenant Lynch in the Dead Sea, 

 Admirals Belknap, Erben, Barker, and 

 Tanner in the Pacific and elsewhere, 

 and Brooke and S. P. Lee in the Atlan- 

 tic. Captain Mahan, our most noted 

 authority on naval subjects, was also 

 an expert hydrographic surveyor. Ad- 

 miral Porter and many of our most dis- 

 tinguished naval officers of the civil war 

 had performed good work in the Coast 

 Survey, and Pillsbury's work in the 

 Gulf Stream is well known. 



CHART CONSTRUCTION 



I shall now briefly sketch the course 

 of chart construction. In general, a 

 preliminar3' sheet of the work done, 

 prepared with accuracy and with a suf- 

 ficient degree of delicate draftmanship 

 to clearly demonstrate any inaccuracies 

 as the work progresses, together with 

 the records of astronomical observations, 

 triangulation, topography, tides, cur- 

 rents, etc., is forwarded from the sur- 

 ve3dng vessel to the Hydrographic Office, 

 where, in the Division of Chart Con- 

 struction, now presided over by one of 

 the most thoroughly equipped hydro- 

 graphic engineers in this or any country, 

 the work is carefully revised in every 

 detail and a smooth sheet prepared, from 

 which comes the working chart, either 

 from an engraved copper plate or by a 

 lithographic process. As soon as the 

 finished chart is printed, all vessels of 

 the Navy serving in the locality which 

 it indicates are supplied therewith. The 

 merchant vessels of all nations can ob- 

 tain it by purchase from the Hj'dro- 

 graphic Office or from any of its numer- 

 ous agents. 



As soon as received in the Hydro- 

 graphic Office, the work is made a mat- 

 ter of record and the history of the chart 

 commences, not to end until the chart 

 becomes obsolete or is canceled by an- 

 other. Every correction, alteration, or 

 addition, with the names of all con- 

 nected therewith, becomes a matter 

 of record which is carefully guarded. 

 While sometimes, for good and suffi- 

 cient reasons, the legend on the chart 

 does not show the authority, that infor- 

 mation is contained in its record. 



GENERAL CHARTS, COAST CHARTS, 

 AND HARBOR CHARTS 



And now let us see what these charts 

 are, what they show, and of what use 

 the3 r are to the mariner. General^ 

 speaking, navigational charts are of 

 three classes — general charts, coast 

 charts, and harbor charts — the coast 



