The _Latitudes_ of the following places: and upon a globe where the longitude is reckoned both ways from the meridian of _London_, their longitudes will be found as follow:
_Latitude._ _Longitude._ Deg. Deg. _Rome_ 41¾ North. 13 East. _Paris_ 48¾ N. 2½ E. _Mexico_ 20 N. 102 W. _Cape Horn_ 58 S. 80 W.
2. _The Latitude and Longitude being given to find the Place._
Seek for the given longitude in the equator, and bring that point to the meridian; then count from the equator on the meridian the degree of latitude given, towards the arctic and antarctic Pole, according as the latitude is Northerly or Southerly, and under that degree of latitude lies the _Place_ required.
PROB. II. _To find the Difference of Latitude betwixt any two given Places._
Bring each of the places proposed successively to the meridian, and observe where they intersect it, then the number of degrees upon the meridian, contained between the two intersections, will be the _Difference of Latitude_ required. Or, if the places proposed are on the same side of the equator, having first found their latitudes, subtract the lesser from the greater; but if they are on contrary sides of the equator, add them both together, and the difference in the first case, and the sum in the latter, will be the difference of latitude required.
Thus the difference of latitude betwixt _London_ and _Rome_ will be found to be 9¾ degrees; betwixt _Paris_ and _Cape Bona Esperance_ 83 degrees.
PROB. III. _To find the Difference of Longitude betwixt any two given Places._
Bring each of the given places successively to the meridian, and see where the meridian cuts the equator each time; the number of degrees contained betwixt those two points, if it be less than 180 degrees, otherwise the remainder to 360 degrees, will be the difference of longitude required. Or,
Having brought one of the given places to the meridian, bring the index of the hour circle to 12 o’clock; then having brought the other place to the meridian, the number of hours contained between the place the index was first set at, and the place where it now points, is the difference of longitude in time betwixt the two places.
Thus the difference of longitude betwixt _Rome_ and _Constantinople_ will be found to be 19 degrees, or 1 hour and a quarter; betwixt _Mexico_ and _Pekin_ in _China_, 240 degrees, or 9⅓ hours.