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To find the difference of longitude, move the perpendicular 
and femicircle to the meridional parts of the given latitudes, and 
the index will cut the difference of longitude on the perpen- 
dicular, 5° 35. ) 3th 
By middle Latitude failing. 
Complement of middle latitude 31° oo. 
Move the femicircle and perpendicular to the given latitudes, 
and the index to the termination of the departure marked on 
the perpendicular, the interfection will fhow the diftance 329 
on the index, and the index the courfe.on the femicircle, 
&. 29° een 
To find the difference of longitude, fet the index to the 
complement of the middle latitude on the femicircle,| and move 
the perpendicular until the departure marked’ on it cuts the 
index, and this point of interfection will mark the difference of 
longitude on the index 335 miles, or 5° 35’. 
C Ae SeEoiboMe 
One latitude, courfe and diftance given, to find the difference 
of latitude and difference of longitude. 
Lat. 56° 40'S. Long. 28° 55" failed from. 
Courfe S. 31° 35’ E.; diftance failed 329 miles. 
By 
