?6 



TERRESTRIAL MAGNETISM. 



[Sect. II. 



and intensity described in 



No 



as well as 



those of the variation by the standard compass, should be 

 made daily, whenever the weather and other circumstances 

 permit. Whenever the ship is in harbour, and time and 

 opportunities -^re suitable, it is desirable that the instru- 

 ments should be taken on shore, to a spot selectt;d as least 

 likely to be influenced by any local attraction : and that 

 the declination, inclination, and absolute horizontal force 



^ 



should there be determined, and the comparative observa- 

 tions made with Fox's apparatus. If the ship has ma- 

 terially changed her geographical position since the last 

 occasion when the deviations vvere ascertained, or if changes 

 have been made in her equipment by which the deviations 



have been affected, it is desirable tliat the procc::. 



mav 



fr 



>Y their examination should be repeated ; and lastly, the 

 hnrbour observations here described should not fail to be 

 repeated whenever the ship finally returns to England. 



Record and Transmission of the Observations. 



12. Blank forms are supplied for the entry of observa- 

 tions of all classes, and for the first or uncorrected cal- 

 culation of those which require that process to be gone 

 through at the time. It is desirable that the forms should 

 be filled up in duplicate, and that one copy should be 

 retained, and the other sent to England from time to 



On 



their arrival they should be immediately examined, and 

 any suggestion to which they may give rise communicated 

 at once to the observer.* 



time, as 



soon a 



circumstances make it convenient. 



* T^i,; 



i iiis has liithcrte been done on all occasions when practicable, and 

 it is very d--!rablc- that it should always continue to be done. 



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!-;ect. U 



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