88 



HYDnOGRAPHY. 



[Sect III. 



Sect. I 



log IS then again put o^ er and the course of the vessel 

 resumed. In this manner the day passes, the hearinfrs 

 and observations all being worked out at the moment 

 the outline run in, views taken, and every particular 



r 



mapped and booked at the time so as to leave nothing 

 to memory. At the close of the day's operations anchor 



sound, and repeat 



n nosition, measure a 



base 



operations as at starting, recall the boats, and in the 

 grey of evening get tlie ship's position by stars and 

 planets, v^hich may at this time be observed with great 

 accuracy before the horizon becomes too obscure. If the 

 ship can remain at anchor, she will observe the set of the 

 stream and the rise and fall of the water, however roughly 

 it may be done. 



As early as possible commit the triangulation to paper 

 that the vessel may start in the morning with some points 

 of land well fixed so as to enable the ship to continue her 



triangulation throughout the day without the aid of the 



boat— although her co-operation as before should be 

 renewed. 



If there be no anchorage, the ship will maintain her 

 position during the night under canvas, and in the grey of 

 the morning picking up the place where she left off on the 

 preceding evening, send the boats away, get altitudes of 

 stars for latitude and longitude, measure a base by sound ; 

 get astronomical bearings and angles, &C.5 and putting 

 over the patent logs continue along the coast as before. 



* 



Thus far we have considered the 



observations as being 

 wholly coniiued to the vessels, but it will add considerably 



For farther informatioa, and a more extensive application of this 

 methed, see Belcher, Mackenzie, and other works on nautical surveying. 



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 charl 

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