Bi, er] 
The difference of longitude is found as in the preceding 
cafe. 
By midale Latitude failing. 
Tur courfe and latitude arrived at are found as above, and 
the difference of longitude as in cafe IV. by middle latitude 
failing. 
GAS E VU 
One latitude, courfe and difference of longitude given, to find 
the diftance and difference of latitude. 
Lat. 48° 30° N. Long. 14° 40’ W. failed from. 
Long. g° 50 arrived at ; courfe S. 35° 26 E. 
By Mercator’s failing. 
Move the femicircle over the meridional parts of the latitude 
failed from, and the index to the courfe, and move the perpen- 
dicular until the difference of longitude marked on it meets 
the index, then the perpendicular will cut the meridional parts 
on the cylinder, which corréfpond with the latitude arrived at, 
then bring the perpendicular and femicircle to the proper lati- 
tudes, and the diftance 345 will be marked on the index by 
the perpendicular. 
N. B. This cafe cannot be performed by middle latitude 
failing ; and in failing on a perallel, or when there is no diffe- 
T2 rence 
