[ 43o ] 
Tn the foregoing experiments, the needle was 
raifed to an horizontal pjfition, and left to vibrate. 
It was between 8 or 9 minutes before the vibration 
ceafed. 
The needle brought to an horizontal pofition, and 
one grain and a half laid on the extremity of the 
South end, was not fufficient to keep it in an hori- 
zontal pofition ; but the North end pointed to 
35" 30'. One grain and three quarters laid on the 
extremity of the South end of the needle, was more 
than fufficient to keep it in an horizontal pofition, 
the South end then pointing 6° 45' below o. 
It having been judged proper to have a Drawing 
of the Dipping-Needle, the following Plate 
[Tab. XIII.] has been made, wherein 
A A Reprefcnts the needle. 
B B The ends of the axis refting on the fri£tion-wheels. 
CCCC The four fri£lion-wheels. 
DDD Where flat agate caps are fet in. 
E E E The divided circle of bell-metal. 
FFFF The ends of the crofs for adjufting the needle. 
GG Two levels, whereby the line of o degrees of the inftru- 
ment is fet horizontal. 
H The perpendicular axis, whereby the inftrument may be 
turned, that the divided face of the circle may front the Eaft 
or Weft. 
I An index fixed to the perpendicular axis H, and which points 
to an oppofite line on the horizontal plate K, when the in- 
ftrument is turned half round. 
LLLL Four adjufting fcrews to fet the inftrument horizontal. 
One of them is hid behind the circle. 
MM MM Screws which hold on the glafs covers, to keep the 
needle ftom being difturbed by the wind. 
INDEX 
