I think the post by Rosemary Payne pretty well sums up the pros and cons of
spire angle measurement. One further bit of information ...

The easiest way to actually take such a measurement is with a little tool
that is easy to make.  You take two strips, perhaps a half inch wide and 4
to 6 inches in length, of a thin but fairly rigid material - sheet plastic,
thin wood or even stiff cardboard.  Lay the two strips flat on top of each
other, with all edges aligned, and press a thumbtack through both strips,
about a half inch from one end.  Turn the strips over so that the point of
the tack is visible.  Press a small plug of cork or wood or cardboard onto
the tack, after adding a small drop of glue to the underside of the plug (or
just surround the base of the tack with glue where it emerges from the
strip).  This holds the two strips firmly together at one end, but not so
firmly that they cannot be moved with respect to each other.  The right
tension will allow you to easily swing the strips apart into a "V" shape,
but will be tight enough to hold the strips where you set them, when you let
go of them.  The "V" can be adjusted to any desired angle, and can therefore
be easily fitted to the spire of a shell (within the limitations described
by Rosemary).  Don't try to get the apex of the "V" tight against the apex
of the shell.  Just fit the two long sides of the "V" against the two sides
of the spire, getting the best possible fit and letting the apex of the
angle fall where it will.  Then just measure the inner angle between the two
strips, using an ordinary protractor.

Paul M.

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