Hey, you gotta be quick witted and nimble brained to keep up with MY tangents, sines, cosines, cotans, etc. As for Nelson's deviance, it was due to the degrees of difference between true North and Magnetic North. If Horatio (as we called him) had known that Magnetic North wasn't True North he wouldn't have discovered Van Dieman's Land, much less Trafalgar and Boothia. AND his crew wouldn't have had to ship him home pickled in brandy, either.