VOL. XXVII.] PHILOSOPHICAL TRANSACTIONS. ggjr 



^f' It may be observed, from the following tables, that the long needle at Q 

 inches from the stone, made somewhat a larger angle than the short needle at 

 3 inches distance from the same; that the short needle at the distance of g 

 inches, made an angle of 9 degrees less than the long one at the same place. 

 But this odds will easily be accounted for, if we consider the disproportions of 

 the needles lengths; for the point of the long needle at 9 inches, was brought 

 within an inch as near the stone, as the point of the short needle was, when 

 but 3 inches distant from the same: the point of the short needle at 9 inches 

 from the stone, was 5 inches further from it, than the long one at the same 

 station. These disproportions being considered, it is no wonder such difference 

 of angles should ensue, by using the several needles near the stone; for at 2 

 feet, and the farther distances, they become nearly agreeable, as before said. 

 In speaking of distances from the needle, I always mean from its centre. It 

 is further observable, that the stone at 5 feet distance from the needle, made 

 an angle of 2 degrees with the one, and with the other of 2 and a half; yet 

 on the absence of the stone, they would return to no degrees, as at first: 

 which plainly shows, that the influence of the stone extended farther; though 

 observations, at remoter stations, could not easily be determined. 



Experiments with both the Needles. 



Distances of the Loadstone The several Angles of the short The several Angles of the long 



from the Needle in Inches. Needle at several Distances. Needle at the several Distances. 



3 87° 00' 



6 8+ 00 



.9 78 30 



12 69 00 



15 56 45 



18 43 30 



21 33 00 



24 24 00 



27 18 00 



30 13 30 



33 11 00 



36 8 45 



39 7 00 



42 5 30 



45 4 30 



48 3 50 



51 3 20 



54 3 00 



57 2 45 



60 2 30 



At greater distances, and even the more remote in these tables, the power 

 of the stone is so weak, and the measuring the angles at all times exactly, so 

 difficult, that it is well if we come sometimes within 10 or 20 minutes of 

 the truth. 



VOL. V. 4 U 



