M. De Witt's Table of Magnetic Variations, S^c. 2S 



The following table exhibits the variation of the compass from 

 actual observation from 1672 to 1800. It was drawn up by 

 John Winthrop, Esq. Mollis Professor of Mathematics 

 at Harvard College in Cambridge. 



T. 



128 years DifF. 5" 53' 5° 53' 



Mean Annual Difference, 2' 45" 28'^ 



NOTE BY THE EDITOR. 



The preceding document, if correct, will be regarded as one 

 of great value by the natural philosopher. When we con- 

 sider, however, that the observations have been made at three 



