Work of the U. S. Hydrographic Office 69 



receiYe and distribute information, vis- 

 iting all incoming vessels for this pur- 

 pose, and hold themselves read}' to ex- 

 -amine charts from any vessel, verifying 

 the same or pointing out necessary cor- 

 rections, examining and correcting in- 

 struments, explaining nautical subjects, 

 and in any way possible giving aid to 

 mariners. In many cases they have 

 even adjusted compasses. At the pres- 

 ent time the officers at three of them are 

 giving night lectures on navigation to 

 shipmasters. Many of these have been 

 called as witnesses in admiralty cases, 

 and in general their influence in im- 

 proving the means of safe navigation 

 has been most marked. A time-ball 

 service is carried on at twelve of these 

 •offices, which is taken advantage of by 

 the masters of vessels possessing chro- 

 nometers, thus enabling them upon go- 

 ing to sea to feel sure of the error and 

 rate of this most important navigational 

 instrument. 



These offices place within almost im- 

 mediate reach of ship captains all the 

 information contained in the main office 

 ■and enable the main office to obtain, 

 with accuracy and quickness, all im- 

 portant information brought by incom- 

 ing vessels. They have been of great 

 benefit to shipping firms, marine in- 

 surance companies, admiralty lawyers, 

 and practically to all interests connected 

 with maritime affairs. 



In 1880 a commander in the British 

 Navy examined the chart outfit of three 

 steamers and found as follows : 



On the first, 73 charts out of 93 

 needed renewal. 



On the second, 39 charts out of 49 

 needed renewal. 



On the third, 95 charts out of 104 

 needed renewal. 



At the present time no vessel need 

 leave a port in which there is a United 

 States branch hydrographic office with 

 incorrect charts unless the captain 

 wishes to do so. 



Other essential aids to navigation are 



published by the Hydrographic Office, 

 but space will not permit of a detailed 

 description. Amongst the most im- 

 portant can be mentioned the American 

 Practical Navigator, a book on naviga- 

 tion which no navigator should be with- 

 out. This is revised frequently and the 

 call for it is continuous. Frequent issues 

 of the Lists of Lights of the World are 

 necessary, the changes in lights all over 

 the world being frequent and often very 

 radical. Azimuth tables for the use of 

 the navigator in determining his com- 

 pass error have been issued by this office 

 for the last twenty-odd years. The In- 

 ternational Code of Signals, which by 

 law all mariners are compelled to have, 

 is an issue of this office. Publications 

 on great-circle sailing ; means of search- 

 ing for isolated submarine peaks ; on 

 the variation of the compass ; sunrise 

 and sunset tables ; illustrated cloud 

 forms ; matters pertaining to marine 

 meteorology and to terrestrial magnetism 

 are amongst the practically useful issues 

 of this office, and all are prepared by its 

 attaches. I can safely state that the 

 great majority of deep-sea vessels now 

 afloat possess some practical aid to navi- 

 gation published by the U. S. Hydro- 

 graphic Office. 



PILOT CHARTS 



The Pilot ■ Charts of the North At- 

 lantic and North Pacific, the permanent 

 issue of which was inaugurated by the 

 Hydrographic Office in 1883, are not 

 navigational charts, strictly speaking, 

 but are simply graphic illustrations of 

 the conditions of winds, currents , wrecks , 

 derelicts, icebergs, fogs, etc., which 

 may reasonably be expected during the 

 month for which the chart is issued. 

 The primary credit for this practical aid 

 to navigation is due to Lieutenant 

 Maury. When, in the early forties, he 

 started his system of collecting infor- 

 mation in regard to winds, currents, and 

 other matters pertaining to the ocean, 

 it was with a view of eventually being 



