Thanks Marty. Guess I got a little excited when I saw the word 'octant' in the records.
I don't actually remember how we sorted it all out.
But the trusty search function
leads me to this pretty excellent paragraph
:P. V. H. Weems,
Air Navigation, 1938, second edition, p. 301:
"Since an arc of 45 degrees is one-eighth of a circle, instruments of this general type, having a maximum angle of 45 degrees between the two reflectors, are known as octants. Instruments having an arc or limb of 60 degrees, or one-sixth of a circle, for measuring the angle between reflectors are called sextants, and those having arcs of 90 degrees, or one-quarter of a circle are called quadrants. Either octants or sextants are suitable for aerial use, but the quadrant is too bulky. For a great many years practically all instruments used by marine navigators for measuring altitudes have been sextants, and the term sextant has become so generally used that it is now applied to all instruments for measuring altitudes of heavenly bodies whether they are actually quadrants, sextants, or octants."
Good arguments can be made either way. The best I can think of against the identifcation of the Niku box as the Manning/Navy box is this: although the word "sextant" could be used for "quadrants, sextants, or octants," it does not logically follow that the word "octant" could be used to stand for "sextant." If the naval telegrams are correct that the instrument loaned to Manning was an octant, and if the investigation in Fiji was correct that the box found on Niku was definitely for a sextant, then it follows that the box found on Niku cannot have housed the instrument on loan to Noonan.
But Noonan may have both borrowed an octant and taken his own sextant. The Niku box does not have
to be the Manning/Navy box in order to be from the fatal flight.
The folks in Fiji who examined the box
reported that it had two numbers on it: "3500 (stencilled) and 1542." We have found quite a large number of boxes with two four-digit numbers on them. Brandis instruments that were collimated by the Navy had a maker's serial number and a Naval Observatory number on them.
If you look on the table of sextant numbers,
there is this little subset:Brandis:Naval Observatory
-- numbers on box found on Niku
Nothing we have found so far disqualifies the box on Niku from having come from Brandis via the Navy. It is an interesting coincidence. It does not seem to me to be entirely inconceivable that the Niku box might have been the Manning/Navy box.