sm 



VARIATION OF THE COMFASS. 



By whom the Variation was observed 



Table of vaiia- 

 tion fcr 22.i 

 years at Lonr 

 ijoE. 



Mr. Burrows* 

 Mr. Gunter 

 Mr. Gellibrand 

 Mr. Bondf 

 Mr. Gellibrand^ 

 Dr. Halle) § 



Mr. Graham|| 



Dr. Heberden^ 

 Mr. Gilpin 



Year. 



Variation. 

 Annual 



Increase 





o 





r 



1580 



11 



15 E 





1622 



6 







+ 1,5 



1634 



4 



6 



9,6 



1657 











10,6 



1665 



1 



22W 



10,3 



1672 



2 



30 



9,7 



1692 



6 







10,5 



1723 



14 



17 



16,0 



174.8 



17 



40 



8,1 



1773 



21 



9 



8,4^ 



17S7 



23 



19 



9,3 



1795 



23 



57 



4,7 



1802 



24 



6 



1,2 



1805 



24 



s 



0,7 



* The observations of Burrows, Gunter, and Gellibrand. in 1634, 

 are-taken from Seller's Practical Navigation, 1676. Burrow'^ obser- 

 vations are said to be the oldest and best in the world; longitude an^ 

 latitude found by dipping-needle, p. xvi. Gellibrand is said to be the 

 first pereon who ascertained the variation of the variation, about the 

 year 1695, Phil. Trans. No. 276—278 ; but if this is the date of the ob- 

 servations by which it was determined, the observations of Gunter, in 

 1662, show him to have a prior claim ; Bond, in his Longitude Found, 

 p. 5 and 6, savs, that the variation was first found to decrease by Mr, 

 John Mair, secondly by Mr. Edmund Gunter, thirdly by Mr. Henry 

 GcUibrg.nd, and by himseir, in 1640. 



-}• Longitude Found, p. 3. 



+ Ibid. p. 13 J and Longitude and Latitude found by Dipping- 

 Needle, p. 6. 



§ Phil. Trans. No. 1 95, p. 5C5. 



11 Ibid. No. 383, p. 107; and No. 488, p. 279. 



f Obligingly communicated by his son, the present Dr. Hebcrder.. 



rah\» 



