By Rare British Maker
Presented is an ebony frame, ivory arc, antique sextant
made by the high quality limited maker Spencer Barrett & Co. of London. It is Ca 1840 – 1850. The octant is in outstanding
condition with finely made metal machinery, and sharply engraved ivory. Most of its original lacquer is intact. It is housed
in a keystone case which is in remarkable condition considering its age, and looks as new inside. A rarely seen special adjusting
wrench is included as is a key.
The arc measures from – 3 to plus 105 degrees. The ivory plate on a cross bar between
the two limbs is engraved “Spencer Barrett & Co. London”.
 
There are many examples of Spencer Barrett instruments in museums, and they are listed in Webster’s
Database of Instrument Makers, but little is known of their history other than they were active between about 1830 – 1880.
A similar example of this instrument in the Smithsonian Museum. See
http://americanhistory.si.edu/collections/navigation/object.cfm?recordnumber=1197564
We previously had an equally magnificent “tulip” framed brass Spencer Barrett sextant, Ca 1870, that
was owned by CAPT E.T. Page.
Spencer Barrett was in business in London from about 1830 to 1880, specializing in instruments for navigational use. There
is no connection between them and the more prolific Spencer Browning & Rust Co. which ceased business in 1870.
This beautifully made instrument has a ribbed brass index arm measuring over 12
inches long with a diameter of arc of 9 5/8″. The horizon mirror is on an adjustable turntable and can be rotated by two knobs
one of which locks the mirror’s position. There are three rectangular sun shades and two circular horizon shades. This sets
this instrument apart from others which were only fitted suns shades. Note the early form thumb screw, ivory vernier scale,
reading from right to left from 0 to 20 arc minutes, two hole peep sight with “flap”, and three sun shades all of which date
the instrument. There is no provision for a handle on this instrument which marks it as a transitional piece between an octant
and a sextant.

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 which indicates it is one of the earliest of that type made by Spencer
Browning making it a noteworthy instrument by this maker.

INSTRUMENT CONDITION: The octant appears in its last
used condition having been owned by someone who lavished great care on his instrument. The mirrors are in much better condition
than might be expected though they do show some age. All the ivory is in perfect condition, and the engraving is sharp and
distinct. The index arm clamp, and shade glasses are complete and in good working order. The ebony frame shows as near new.
The instrument has its original machinery, and a two hole peep sight. Everything is original and in good working order.

THE CASE: The “keystone” solid Mahogany case is in
excellent condition overall, and very clean inside. It has one small age crack, and a small missing piece at one corner on
the bottom. There is a lock, and key.
                    
Maker’s Name
                   
Vernier scale
          Peep sight and horizon mirror
                
Machinery and index mirror

All in all,
a highly desirable and worthwhile example from one of the higher quality English instrument makers.
DIMENSIONS:
Length of frame 12″
Width of frame at arc 9 5/8″
Index mirror 50 x 30 mm
Horizon mirror 24 x 20 mm
Weight 2 Lbs 2 oz
 
CREDENTIALS: We are one of the few people selling
Old World navigation instruments that know anything about them. For purposes of judging whether my opinion counts, I 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.
I am also a retired Master Mariner, and formerly held a U.S. Navy “D” Qualification as a Senior Skipper- Oceans.
Rarely do you find an instrument that is that
is 166 years old in this original condition with a perfect case. A superior
addition to any collection.