Oil lln: Force of Magnet iam. 375 



consideration, as having been made under more favourable cir- 

 cumstances than were presented by the other opportunities of 

 the voyage ; they are, therefore, to be compared with those wliich 

 were made in England. 



" The dip in London being 70° 33'.3, and at Winter Harbour 

 88° 43.5, the force in the direction of the dipping needle 

 should increase by calculation in the ratio of 1,153 to 1. 



" The time of vibration of Mr. Browne's dipping needle de- 

 creased, between London and Winter Harbour, in the proportion 

 of 481 to 446, and consequently the force appeared to have in- 

 creased in the ratio of 1 .163 to 1. 



" The dip at Sheerness being 69° 55' , and at Winter Harhour 

 88° 43'.5, the magnetic force should increase by calculation 

 as 1.163 to 1 ; but the force acting on the horizontal needle 

 should be diminished in the proportion of 13.275 to 1. 



" The times of vibration of the three horizontal needles in- 

 creased between Sheerness and Winter Harbour, in arcs from 7 

 to'14 degrees, respectively, as follow : No. 1 as 339.7 to 94.5 ; 

 No. 2 as 327.4 to 90 ; and No. 3 as 316.1 to 85 ; consequently, 

 the force acting on them appeared to have diminished by No. 1 

 as 12. 93 to 1 ; by No. 2 as 13.23 to 1 ; and by No. 3 as 13.83 

 to 1 ; the mean being as 13.33 to 1 ; differing but ^-^^^ from the 

 result of the calculation. 



" This is, perhaps, a nearer agreement with the theory than 

 there was reason to have expected, considering how much the 

 unavoidable causes of uncertainty in such experiments are aug- 

 mented in high magnetic latitudes. 



" The results on the 26th of June, and on the 23d and 24th of 

 July, 1819, compared with the observations in England, will 

 also be found to agree as well with the theory as it is reasonable 

 to expect in experiments, where neither time nor circumstances 

 admitted the adoption of the precautions, requisite to ensure 

 the utmost accuracy of which they are capable ; and where, 

 perhaps, the moving of the ice during the observations may 

 have introduced an additional error which no care could guard 

 against. By the experiments of the 26th of Juno, the force 

 tad diminished by Needl*? No. 2, as 2.815 to 1, uud l?y No. 3 

 •i C 2 



