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I wouldn't be too critical of Mary Blewitt's Book. A lot of
things are "wrong" but in a sense still work.

My uncle read Blewitt's book and sailed from Bay Saint Louis, MS
to Cozumel, Mexico and back. This was before GPS and stuff. He had been
coast sailing for years to FL and so on, but this was his first big open
ocean trip. He made it just fine.

This reminds me when I had a small part-time job helping out in
a hospital. I had a friend did urine tests. She put a little
bit in a test tube and then put in a test strip. If it turned
blue it meant this, and if it turned red it meant something else
and so on. Neither she nor I knew how it worked, or what we
were doing, but it got the job done.

Spherical Trig is not really taught in regular college math
classes. The university where I got my Master's in Math had
no such classes. If you wanted to learn spherical trig you were
on your own. Spherical triangles are hard ( for me ) to visualize
and the formulas are long, unfamiliar and complicated. They are
made more complicated because in the era before calculators,
they did everything to make hand calculations with logs and
tables "easy". Take for example the Law of Cosines for plane
trig: cos^2 = a^2 + b^2 - 2ab cos B, I quote from "Trigonometry
for Navigation Officers" by W. Percy Winter (1928) concerning the
law of cosines,

"The student will see that the process is both
lengthy and cumbrous; for that reason the cosine law is said to
be not adapted to logarithmic computation."

Today, the law of cosines is no problem with a calculator, so there
would be no need for an alternate.

There is a place for simple hand waving books. Bluewitt's audience
is not the professional navigator, mathematician, or even the
advanced amateur, but it gets the job done.

The first book I read on Navigation was when I was 14. It was
called "How to Navigate Today". I forgot the author, but I
think it is still in print. It is along the same lines a Blewitt's.

Gordon

PS: The best "simple" books I have found are books written for the
war effort in WWII, both in Britain and the US. They needed mass
amounts of people competent in navigation and fast. They couldn't
spend 4 years in college learning the stuff, they needed navigators
in 6 mo. or less. They trimmed the fat and cut to the essence of
what was really needed.

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| Gordon Talge WB6YKK         mail: gtalge AT silcon DOT com |
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