[ 477 ] 



meridian. The two needles were nearly balanced 

 before they were made magnetical; but, by a curious 

 contrivance of the Reverend Mr. Mitchell of a crofs 

 fixed on the axes of the needles (on the arms of 

 which were cut very fine fcrews, to receive fmali 

 buttons, that might be fcrewed nearer or farther from 

 the axis), the needles could be adjufted both ways, 

 to a great nicety, after they were made magnetical, 

 by reverting the poles, and changing the fides of the 

 needle. 



Firft fet of experiments made by Edward Nairne, at 

 his houfe, N° 20, Cornhill. 



72 20 

 72 20 

 72 20 

 72 20 

 72 20 

 jz 20. 



Second fet of experiments, with that fide of the in- 

 frrument to the Eaft, which was to the Weft in 

 the firft obfervation. 



72 10 



7 2 J 5 



72 45 1 Here the ends of the axis touched the 



72 45 J agates, 



72 5 



72. 



Third 



