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1602 H. Briggs (title) A table to find the height of the Pole; the magnetical declination being given.]

1787 J. Lorimer Let. in T. Cavallo Treat. Magnetism App. 339 From 1657 at London, and 1666 at Paris, a west declination began, and has ever since increased, gradually though not uniformly, or in the direct proportion of the times; for such is the nature of the magnetic declination.

1814 P. Barlow New Math. & Philos. Dict. at Variation M. Burckardt, an ingenious French astronomer, invented a formula to represent the magnetic declinations observed at Paris.

1830 Philos. Trans. (Royal Soc.) 120 101 The disturbance of the magnetic declination by the northern lights on the evening of the 14th December [1829] was so great.., as to leave no shadow of doubt regarding the reality of the phenomenon.

1849 Trans. Royal Soc. Edinb. 19 ii. p. xviii The probable error of an observation of magnetic declination..is least in June.

1966 McGraw-Hill Encycl. Sci. & Technol. (rev. ed.) IV. 20/1 One of these [components], called variation by the navigator and magnetic declination by the magnetician, is the angle between magnetic and geographic meridians.

1997 Irish Times (Nexis) 5 June 2 A consequence of this meandering of the pole is that the magnetic declination, the angle between the ‘true’ north and ‘magnetic north’, is continually changing.