Work of the U. S. Hydrographic Office 65 



■charts occasionally being divided into 

 special and general. 



General charts, as the name implies, 

 cover a large territorj^, and are princi- 

 pally for the use of navigators in the 

 open sea, as in making long voyages. 

 This class of chart is necessarily upon 

 a small scale, and represents not only 

 the character of the ocean bed as thus 

 far delineated by deep-sea soundings 

 obtained b}' vessels of the principal 

 maritime nations, but also the shore 

 lines with the most prominent topo- 

 graphical features, the principal sea- 

 ports, the lighthouses which are of use 

 in off-shore navigation, all dangers in 

 the nature of shoals, reefs, and rocks, 

 and the lines of equal magnetic declina- 

 tion or variation; compass stars, show- 

 ing both true and magnetic directions in 

 degrees and quarter points, are placed 

 where it is thought they will be of the 

 greatest use. On this chart the navi- 

 gator plots his geographical positions as 

 often as they are determined, and thus 

 is able to keep as nearly as possible a 

 direct course to his port of destination. 

 This chart is kept in use until the vessel 

 gets within the limits of the coast chart, 

 when it is put away and replaced by the 

 latter. 



Coast charts, both general and special, 

 delineate the coasts of all countries, and 

 for each coast are consecutive and take 

 in such sections of the coast as will per- 

 mit of the use of a comparatively large 

 scale. The coast line is accurately de- 

 lineated, as are also the principal topo- 

 graphical features which can be used in 

 navigation; all the lighthouses, with 

 their peculiar characteristics; the life- 

 saving stations, Weather Bureau sta- 

 tions, and all the features which in any 

 way can enable an observer by bearings, 

 or otherwise, to determine his position. 

 The soundings are frequent and, in gen- 

 eral, are run out to the ioo-fathom 

 curve. With the aid of this coast chart, 

 the navigator pilots his ship along shore 

 until withiu the limits of the chart of 



the harbor to which he is bound, when 

 that replaces it. 



The harbor chart is on a larger scale 

 than the others and in greater detail. 

 Every object on shore that can be used 

 in piloting the ship in or out of the har- 

 bor is delineated in its correct position. 

 Where possible, ranges to guide vessels 

 in and out are determined and plotted 

 upon the chart ; lighthouses, range 

 lights, buoys, beacons, and all day- 

 marks are plotted; the positions of land- 

 ing places, custom-houses, and public 

 buildings of which the navigator may 

 have occasion to know are plotted, 

 where possible; curves of certain equal 

 depths of water, quarantine stations and 

 quarantine grounds, men-of-war and 

 merchant ships' anchorages are also 

 clearly indicated; the magnetic declina- 

 tion or variation is noted on one or more 

 compass roses, and in addition the chart 

 contains all necessary data as to the date 

 of publication, the date of the latest cor- 

 rection, the character of the soundings, 

 heights, signs, and abbreviations, and 

 all necessary tidal information. On 

 these charts, as on coast charts, the 

 shore lines are made especially conspicu- 

 ous, and the topographical features rep- 

 resented are such as will be of actual 

 value as aids to navigation. 



USE OF SURVEYS BY OTHER NATIONS 



I have only referred to original sur- 

 veys by our own vessels ; but it must 

 not be understood that the chart con- 

 struction work of the Hydrographic 

 Office ends with these. We all realize 

 that in time of war it would be a diffi- 

 cult matter (perhaps an impossible one) 

 to get correct navigational charts of 

 foreign places against which our Navy 

 might have to operate, and during peace 

 periods it takes time to obtain the latest 

 editions of foreign charts. All the great 

 maritime nations recognize the fact that 

 it is a matter of national moment for 

 them to be possessed of all available 

 charts of every part of the world, and 



