An introduction to astronomy: designed as a text-book for the use of students in college. By Denison Olmsted ...

24 THE EARTH.
great circle, the 90th degree will reach to the circumference of
that circle, and being therefore a great circle passing through
the pole of another great circle, it becomes a secondary to the
latter. (Art. 21.) Thus the quadrant of altitude may be used
as a secondary to any great circle on the sphere; but it is used
chiefly as a secondary to the horizon, the point marked 90~
being screwed fast to the pole of the horizon, that is, the
zenith, and the other end, marked 0, being slid along between
the surface of the sphere and the wooden horizon. It thus
becomes a vertical circle, on which to measure the altitude of
any star through which it passes, or from which to measure
the azimuth of the star, which is the are of the horizon intercepted between the meridian and the quadrant of altitude
passing through the star. (Art. 27.)
66. To rectify the globe for any place, the north pole must
be elevated to the latitude of the place (Art. 43); then the
equator and all the diurnal circles will have their due inclination in respect to the horizon; and, on turning the globe (the
celestial globe west and the terrestrial east), every point on
either globe will revolve as the same point does in nature; and
the relative situations of all places will be the same as on the
respective native spheres.
PROBLEMS ON THE TERRESTRIAL GLOBE.
67. To find the Latitudee and Longiitude of a place: Turn
the globe so as to bring the place to the brass meridian; then
the degree and minute on the meridian directly over the place
will indicate its latitude, and the point of the equator under
the meridian, will show its longitude.
Ex. What are the Latitude and Longitude of the city of New
York?
6S. To find ca place having its latitude and longitude given:
Bring to the brass meridian the point of the equator corresponding to the longitude, and then at the degree of the meridian
denotingl the latitude, the place will be found.
Ex. What place on the globe is in Latitude 39 N. and Longitude 77 W.?