TABLE 3. 
Difference of Latitude and Departure for 17° (163°, 197°, 343°). 
In Plane Sailing. 
For converting Dep. into Diff. Long.and Diff. Long.into Dep. 
In Middle Latitude Som. ue 
For converting Dep.into Diff. Long. and Diff. Long.into Dep. 
In Mercator Sailing. 
For multiplication of numbers by sines and by cosines, or 
solution of plane right-angled triangles. 
