314 Variation of the Magnetic Needle at Providence, R. L 



Art. VII. — Variation of the Magnetic Needle at Providence, 

 R. L, from A. D. 1717 to 1843; by M. B. Lockwood, Civil 



Engineer. 





The following table, showing the magnetic variation, nearly } 

 for the last one hundred and twenty six years, has been con- 

 structed from actual observation, from observations on record, 

 and from the recorded bearings of a very great number of per- 

 manent objects at various periods. 



For example, Richard Jackson, on a map of a part of Provi- 

 dence, states the variation in 1717 at 9° 36 / W. In 1769, at the 

 transit of Venus, it was carefully ascertained by Dr. B. West to 

 be 6° 30' W. In 1815, Moses Brown, Benoni Lockwood, and 

 George Sheldon, agreed by different methods in making it 6° 

 30" W, In 1819, Friends' Boarding School edifice was erected, 



fronting the magnetic south ; from which, the variation at that 



time is ascertained to have been 6° 37' W. Since 1835, the va- 

 riation has been obtained by careful observation. 



It is not to be supposed that the accompanying table is correct 

 to a minute, so imperfect were the instruments used during most 

 of this period ; yet from a great diversity of trials, where the 

 bearings recorded are known to have been made by different in- 

 dividuals, the error can in no case be large. 



Y 



ears. 



1717 



1720 

 1725 

 1730 

 1735 

 1740 

 1745 

 1750 

 1755 

 1760 

 1765 

 1769 

 1775 

 1780 

 1785 



Magnetic variation, 



9° 36' w. 



9 28 



9 14 



8 54 



8 39 



8 15 



7 59 



7 40 



7 21 



6 57 



6 43 



6 30 



6 20 



6 16 



6 13 



Years. | Magnetic variation 



1790 

 1795 

 1800 

 1805 



1810 

 1815 

 1819 

 1825 

 1830 

 1835 

 1840 

 1841 

 1842 

 1843 



6° 10 

 6 10 

 6 15 

 6 19 

 6 24 

 6 30 



6 37 



6 51 



7 10 



7 34 



8 25 

 8 31 

 8 39 

 8 46 



w. 





Providence, January 1, 1843. 



