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



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

 R. I., 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. 



Providence, January 1, 1843. 



