for ascertaining the Deviation of the Magnetic Needle. 371 



by the sun's bearings, and found to vibrate freely : when the 

 face of the instrument was directed to the East or West, the 

 mean dip it gave was 80° 37' 50"; when the instrument was 

 removed from the North-west to the South-east point, about 

 twenty yards distant, and placed on the meridian, the needle 

 ceased to traverse, but remained steady at an angle of 60° ; 

 on changing the face of the instrument so as to give it a South- 

 east and North-west direction, it hung vertically. The posi- 

 tion of the slaty strata of the magnetic ore is also vertical,— 

 their direction is extremely irregular, being much contorted. 



— Page 56. , 



« The observations of this evening seem to corroborate the 

 remark which I had previously made, that the direction in 

 which the needle moves seems to depend upon the position in 

 which the streams of the aurora borealis are placed, and the 

 quantity of its effect to its proximity to or distance from the 

 earth. When the extremities of the arches lay near the bear- 

 ings of 324° and 54°, the needle moved Eastward ; and when 

 near the bearing, 324° and 144°, or 279° and 99°, the motion 

 of the needle was Westward: both of these facts were shown 

 to-nifxht. At the first display, when the extremities ot the 

 arches pointed near 324° and 54°, and the interior motion lol- 

 lowedthe same direction, the needle moved Eastward as tar as 

 345°, but after midnight, coruscations ceased to appear m that 

 direction, and at 12" 10™, were Presented in three arches 

 traversing the zenith, whose extremities pointed 1 2 1 and 302 ; 

 the needle then receded towards the West, and rested at 349 

 SC, having varied its position 5° 40' in the course ot twenty 



minutes." — Page 560. , . . , ^^ c a,^ 



« I apprehend much of the irregularity in the result ot the 

 observations for the variation of the compass along the Copper 

 Mine River is to be attributed to local causes ot attraction, 

 and particularly to the existence of iron ore among the rocks, 

 which is very general : a greater intermixture of iron ore was 

 perceived in the rocks on the sea coast, than on the banks ot 

 the Copper Mine River."— Page 635. 



♦' The seat of the phenomenon of the aurora boreahs lies 

 between the latitudes 64° and 65° North, or about the position 

 of Fort Enterprize, because the coruscations were as often seen 

 there in the southern as in the northern parts ot the sky. — 



^fhelJland of Canna, on the western coast of Scotland, 

 affords a remarkable instance of the ellects on the magnetic 

 needle from the local attraction of mountams (charged with 

 iron ont).—Sce Munai/s 'I'our to the Ilchrides. 



^ A 2 LVIII. A Binary 



