exactly in. the nortb point of the heavena : but, for
the sake of illufitratiag the subject, we wiU $uppos«e
that it is, and 3ee what will follow from it3 having
this situation,

IrfCt N3, (PI. IV, fig. 9.) tberefwe, be the axis of
the earth, prod uced to the polar star p ; £a the
equator, and % the zenith, or place of observation i
then, since zo, the distance of the zenith from
the horizon, b ninety degrees ; and ne, the dis-
tance of the pole froip the equatior, is aUo ninety
degrees; the arc o% will con^quently be equal to
the arc N)s; wd if the arc nz, whioh is cominoii
tp tbe9) both, be taken away, the remainder
oir, will be equal to the remainder ze: but o if
is the height of the pole above the horizon,
and %% \% the latitude of the place, pr its dis^
toPCe from the equator; and therefore, if the
height of the pole above the horissoo be takeo by
means of a quadrant, or asy other instrumeat
proper for the purpose, it^will evideatly give the
latitude of the place where the observation wa$
ii^ade. Thus, the height of the north pole at
XiOndon is found to be about fifty-onc degrees^
thirty- two minutes ; and therefore this 13 the latir
tude of the place, or its distance north from the
equator. (A)



(A) The only thing thftt eaq Btund ia aeed of fiirtber aiuB?*
tration on this head is> th^t it may not a|^ear, at iSi^t 6l^bt»
bow a person standing on the surface of the earth at z, c^n
measure the angle nco at the centre^ or the altitude
of the polar star 01^5 but this seeming difficulty vanishe:^,
wh«n we consider the immense distaoco.of this.fix«d jt2M%» t»



X^ET. IX.] LATITUDE AND LONGITUDE. 