[ 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 fmall 
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 reverfing the poles, and changing the fides of the 
needle. 
Firfl fet of experiments made by Edward Nairne, at 
his houfe, N° 20, Cornhill. 
o / 
72 20 ’ . ' r : 
72 20 - ; V 
72 20 .V ... ' 
72 20 
72 20 
72 20. 
Second fet of experiments, with that fide of the in- 
ftrument to the Eaft, which was to the Weft in 
the firft obfervation. 
72 10 
7 2 
72 45] Here the ends of the axis touched the 
72.45/ agates. 
7 2 5 „ 
72 - 
Third 
