APP. M° IX.] MAGNETICAL OBSEIIYATIOXS. 537 



fortieth, and every seaman from a one hundred and fortieth 

 to a two hundredth part of the neat produce. 



No. IX. 



ON THE ANOMALY IN THE VARIATION OF THE MAGNETIC 

 NEEDLE, AS OBSERVED ON SHIP-BOARD. By W. ScORESBY 



jim. Communicated to the Royal Society of London by 

 the Right Hon. Sir Joseph Banks, Bart. G.C. B. P. R. S. 



Read Feb. 4. 1819. 



The anomahes discovered in magnetical observations con- 

 ducted on ship-board, were usually attributed to the imper- 

 fection of the azimuth compass, until Captain Flinders, in 

 his modest and enlightened paper on this subject, pubUsh- 

 ed in the Philosophical Transactions, suggested that they 

 were probably owing to the magnetic influence of the iron 

 made use of in the construction of the ship. The truth of 

 this suggestion, and the accuracy of his observations, have 

 since met with full confirmation, and some of his practical 

 rules founded thereon have received additional support, from 

 the " Essay" of Mr Bain, " On the Variation of the Com- 

 pass," lately published. 



As I have been materially anticipated by Mr Bain in a 

 series of observations on the variation of the compass, which 

 I conducted on the coast of Spitzbergen, in the years 1815 

 and 1817, it will be unnecessary here to enter into the 

 detail of these observations, or enlarge upon the probable 

 cause of the anomalies observed ; it may be sufficient to 

 give a table of the most accurate of my observations, and 

 annex to it the few general inferences which were drawn 

 from it, during the voyage in which most of the observa- 

 tions were made, (1817,) together with such remarks on each 

 inference as seemed to me calculated for its elucidation. I 

 shall, however, just premise, that I am not unconscious of the 

 great liability to error in observations of this kind, and of 



