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Sir Howard Douglas navigational quadrant for sale on eBay

A rare navigational instrument signed 'Cary, London', patent 73, dating from around 1825.As a result of clever design, this instrument can be used to take instantaneous sightings of objects separated by up to 120 degrees, so facilitating a rapid determination of a given position.
The 110mm. Linear plotting scale under the semi-circular scale (reading to one minute of the arc) is divided in units of ten from 0 to 1760, the interpolation grid being divided every single unit.
This instrument was invented by Sir Howard Douglas of the Royal Military College at Farnham and is essentially a combination of both Hadley's quadrant and a protractor.
Thus angles can be plotted directly without recourse to the reading of angular scales.
The instrument measures 145 mm. X 192 mm.
The radius of the semi-circle is 54 mm.
The box measures 110 x 168 x 46 mm.
The instrument retains the majority of the original finish and is in very good order.

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Comment by Russell Lynn Drysdale on June 8, 2011 at 2:38
I wish i had the Cash , I would take that off the market .

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'My great-grandmother mother was a Douglas from Montrose' does not give many clues to follow up! But a bit of flesh on the bones makes further research possible. But if we are told who she married, what his profession was and where the children were baptised, then we can get to work.

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