Presented is a museum quality, a term we don’t use
often, ebony frame, ivory arc, antique sextant made by  Spencer, Browning & Co. of London, Ca 1840.
It is fitted with a peep sight making it an early example from the first half of the 1800’s. It is in remarkable
original condition and has the label of Samuel Thaxter & Son, No. 125, State St., Boston which is also in excellent
original condition. 
The arc measures from – 5 to plus 105 degrees. The ivory plate on a
cross bar between the two limbs is engraved “Spencer Browning & Co. London”, Additionally, in the center of the ivory
degree’s scale is inscribed in script “SBR”, between 50 and 55 degrees, identifying the ivory was engraved
by Spencer, Browning of London.
THE INSTRUMENT: This beautifully made sextant has a ribbed
brass index arm which measures 12 inches long. Note the thumb screw, early form ivory vernier scale, reading from
right to left from 0 to 20 arc minutes, a movable peep sight, and a set of three sun shades. The
horizon mirror is on an adjustable turntable and can be rotated by an arbor. There is no provision for a handle on this sextant
which with the other indicators all of which help date the instrument as a transitional piece between an octant and a
INSTRUMENT CONDITION: The sextant has been recently polished
and lacquered in order to emphasize the quality of its workmanship. The ivory pad on the back of the frame is missing
as is the original ivory pencil holder. The mirrors, though showing their age with hazing are in good condition and the
shade glasses are like new. The ivory arc is in perfect condition, except for some age spotting at the left end. The
engraving is sharp and distinct. The index arm clamp and tangent screw are complete. Everything is in good working order. The
entire instrument and ebony frame shows as near new. The instrument has its original machinery, and a two hole peep



    “SBR” imprint at 55 degrees
mirror and shades
sight and horizon miror


THE CASE: The “keystone” is Mahogany
with one minor repair in the lower right corner where a piece of wood has been replaced. The top is slightly warped. It is
in otherwise good and strong condition. It does have an age crack on the bottom. It has been refinished. There
is a lock, but a the key is missing. A label of Samuel Thaxter & Son, No. 125, State St., Boston which is
also in excellent original condition is inside.

in case showing Thaxter label on lid


Spencer Browning Rust worked in London from 1724 to 1840 when the name
was changed to Spencer Browning & Co. after the death of Ebenezer Rust.  The successor, Spencer Browning had
offices at a number of addresses on Wapping High
Street, London and were in business until 1870. They had an early dividing machine and
inscribed arcs for others.
Ref: Gloria Clifton, Directory of
British Scientific Instrument Makers 1550-1851
(London, 1995), p. 261.



label in the case is of Samuel Thaxter who was born in Hingham, Massachusetts in 1769 and died 1842. He apprenticed to William
Williams, maker of a backstaff in 1768 with a King Street, Boston address. Upon Williams’ death in 1792 Thaxter took over
the nautical instrument making business, moving to Long Wharf, State Street, Boston in 1792. His address was first advertised
as “Head of Long Wharf”. During the 18th century, prior to the advent of street numbers, a business location was quite often
identified by a landmark, such as “At the sign of the Little Admiral” or “Head of Long Wharf.” Ref.
From Webster’s Registry of Instrument Makers, (1792); 125 State Street (1796-1842);
both in Boston, Mass.”

He is first listed in the 1796 Boston
Directory as a mathematical instrument maker.  In the 1822-23 edition, the business is listed as Samuel Thaxter &
Son (Joseph H. 1801-1835).  Samuel Thaxter’s grandson, Samuel Thaxter Cushing (1821-1882), took over the business around
1843. Upon the death of Samuel Thaxter Cushing, his widow, Abby C. Cushing took over management of the business until 1905
at which time Herbert Risteen Starratt became manager.  The last entry of the company (Samuel Thaxter & Son) in the
Boston Directory is 1916.”
Ref.  Smart, Charles
E.   The Makers Of Surveying Instruments In America Since 1700  Troy, New York:  Regal Art Press.


A highly
desirable and worthwhile example from one of the better known English instrument makers, and sold by Samuel Thaxter, one of
America’s early and finest instrument makers

                   Classic style keystone case with slight warp to top

Some time after 1780, the addition of a tangent screw, as fitted to this
instrument, allowed for fine adjustment and represents one of the two major changes in the basic operation of the octants
and sextants for the next 150 years! The second was the fitting of telescopes. As was the practice with octant’s of larger
size, this sextant was not fitted with a handle or a telescope indicating it is one of the earliest of that type made by Spencer
Browning making it a noteworthy instrument by this maker. This is also confirmed by the Thaxter label, since Samuel died
in 1840.





Length of frame 12″
Width of frame at arc   9 5/8″
Index mirror       44 x 32 mm
Horizon mirror 32 x 22 mm

Weight sextant   2 Lbs 2 oz


QUALIFICATIONS: We are one of the few company’s still selling navigation
instruments that know anything about them. For purposes of judging whether Joel’s opinion counts, he was the editor
of the chapter on sextants of the 1977 Edition of “Bowditch”, The American Practical Navigator, NAVPUB 9; a member of the
U.S. Naval Academy Navigation Symposium Board, 1975 -1978; the author of a book on marine sextants, Cornell Maritime Press,1975,
and the founding president of Nautech Maritime Corporation which partnered with Tamaya of Japan in the introduction of the
MS 733 Spica, the MS 833, Jupiter, MS 933 Venus sextants and the famous NC-2 navigation computer, in the U.S. market. Joel
is a retired Master Mariner, and held a U.S. Navy “D” Qualification as a Senior Skipper – Oceans.
six years he was a Varsity Offshore Coach at the U.S. Naval Academy.
Rarely do you find an instrument that
is that is 169 years old in this original condition with a perfect historic label. A superior addition to any collection.

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