^ 



41 



Sect. III.] 



HYDROGRAPHY* 





1 • IJ.- 



J 



ut 



u- 



b -"'^ 



F 



i 



^ 





1 



0{X 



f 



t"^- 



i - 



?e, 



an additional interest attaches to a correct knowledgs 



■■^ 01 



them. The su-iraan should therefore not only carefully 

 note the direction and force of the winds^ but should 

 connect with such entries notices as to when and where 

 any continued or periodic wind commenced and termi- 

 nated : what was its strength and effect upon the pas- 



came on suddenb^ 



J5 



and was furious 



sage; whether it 

 while it lasted, or otherwise ; whether It was preceded by 

 any particular symptoms, and whether it was such as 

 usually occurs at that season ; and lastly, w^hether it he 

 advisable to cross this wind in any particular direction, 

 such as close hauled or large, &c. 



2. To detect the current, a more than ordinary atten- 

 tion must be paid to the reckoning of the ship : the 

 compass by which the course is steered should occasionally 

 be compared with that by which the variation is deter- 

 mined, in every position of the ship's head :* and the 

 ship's place should be determined by observation at least 

 once a day. Sights for chronometer morning and even- 

 ing should both be referred to noon, at which time 

 the latitude will of course be observed ; and all observa- 

 tions for latitude at night, or for fixing the ship*s place 

 at any time, should be referred to one period of the day, 

 in order that the position of the ship bi/ ohservation^ as 



Dead 



may 



give the direction and force of the current, if any, 

 for the twenty-four hours. These observations should 

 all be entered in a table, and at the close of certain 

 obvious and natural periods of a passage, such as that of 

 entering or emerging from the trade-wind, the calm lati- 



* See Section * Terrestrial Maa:netism; 



I- 



