I've obtained this octant in 2001. The octant was the successor of the cross-staff and backstaff instruments like the Davis quadrant and the predecessor of the sextant and quintant. The term 'octant' comes from the fact that the instrument's arc covers 1/8^th of a circle or 45º. The use of the mirror on the index arm multiplies this by 2, so an angle of up to 90º can be measured.

Although the octant was the first successful double reflecting instrument it was not the first reflecting navigational instrument. The first navigational instrument equipped with a mirror was the spiegelboog, invented in 1660 by the Dutchman Joost van Breen.

The octant was invented in 1731 by John Hadley. Before Hadley others too invented reflecting instruments, like Robert Hooke in 1666 (a single reflecting instrument) and Sir Isaac Newton in 1699 (a double reflecting instrument), but these never became widely used.

Possible owner was Captain Denison (sometimes spelled with two 'n's), master of the brig Mary Stewart (see figure 2) in 1858.¹

The brig Mary Stewart was built by T. Crosby in Bangor, Maine in 1856 and owned by T. Stewart of Bangor.¹ The painting at the left shows what the Mary Stewart looked like when she was a brig. Below, figure 19 shows her after she was re-rigged to a schooner around 1875-76.

A Capt. J. W. Dennison (spelled with 2 'n's, but either the register or the spelling on the lid could be wrong) was master of a brig Mary Stewart in 1858. Although spelled differently and the fact that more ships did exist bearing that same name, there is a fair change that it was this vessel on which the octant was used.

The lid also bears a date: 11/10/48, followed by a capital D. This could well be 10 November 1848, 10 years before Denison became master of the brig.

In the lid the trade card of Frederick W. Lincoln is pasted over the trade card of Aaron Breed. Although both of them are American, being made of oak, the keystone box would be British (and so would be the instrument when it belongs to the box).

Frederick W. Lincoln (b. 1817), a grandson of Paul Revere, was apprenticed to Gedney King, instrument maker of Boston, in 1830. Lincoln set up in business in 1839, and until 1853 was at 62 Commercial St., and then until 1856 at 136 Commercial St. In 1858 one of his apprentices, Charles C. Hutchinson, became a partner, and it was at this point that the firm became known as Frederick W. Lincoln, Jr. and Co. and moved to 126 Commercial St.¹

In 1848, Aaron Breed, mathematical instrument maker, lived at 138 Purchase Street in a building owned by Jotham Bush. His shop was located in the building at the corner of Broad and Purchase Street owned by Frederick Clapp. His shop was in the same location in 1847 and 1849. The earliest tax records we have here at the City Archives are from 1822. Aaron Breed was listed in 1822 as a "Jy Mathematical Instrument Maker". In 1823, he had a shop at India Wharf and Broad Street. The latest occurrence of him dates from 1860. He was then listed at 1 Lincoln St. as a "Gentleman". At the same address, George W. Choate, "Jy. Mathematical Instrument Maker" was also listed.²