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THE VOYAGE OF H.M.S. CHALLENGER. 



7. — Abstract of the Constants of 



The notation on this page is that of the "Admiralty Manual" for deviations of the compass, 4th ed. 1874, 

 with the exception of A', for which see Magnetieal Instructions. 



The horizontal component of the ship's magnetic force proceeding from sub-permanent magnetism is denoted 

 by the constant parameters P and Q ; P the force towards tin' how ; Q the force towards the starboard side. 



That part of the horizontal component proceeding from transient induction in vertical iron is represented by 

 the constants c and/'; c the force towards the bow ; /towards the starboard side. / has no appreciable value 

 in the Challenger, and is therefore not quoted in this table. 



These constants are expressed in terms of the earth's horizontal force at Kew Observatory = 1 '0. 



