The Ball Recording Sextant
A most unusual instrument. It was designed
and originally made by the Mergenthaler Linotype company for the
US Navy. This is the same company that produced Linotype machines
for the printing industry. Later it was produced by David White
Co., and in fact most instruments I have seen bear David White's
name on the body.
The upper photos show a David White
instrument which is in many respects a conventional Marine sextant
with the Ball Recording attachment added. The lower shots are
of an original Mergenthaler Linotype instrument, the photos from
the official operators manual..
The large tube with a clear top contains
nine steel balls of 5/32" diameter. These are released by
a trigger and theoretically fall vertically. There is a marking
device at the bottom of the tube which enable an average reading
to be obtained.
Official tests of these instruments
have shown them to be rather inacurate even in the hands of a
good operator. I don't think this principle has been used by any
other instrument, though there was a development of this one and
even a serious attempt to improve its accuracy. The fact that
it remains a rather rare device points to the fact that it was
of little practical use.
Here is an extract of part of the "Notes"
issued in the user manual.
""IN ANY CASE IN WHICH THE
SAFETY OF THE SHIP IS INVOLVED, SOLE RELIANCE SHOULD NOT BE PLACED
ON DATA FROM OBSERVATIONS WITH THIS INSTRUMENT.""
Booklet
Back to Other
Sextants