18th Century, 18 inch Hadley’s Quadrant (octant) – Francis Fitton, Cork, Ireland

18th Century, 18 inch Hadley’s Quadrant (octant) – Francis Fitton, Cork, Ireland

Stock Number: NM. 2-28

poa

An historical interesting three mirror octant, made by Francis Fitton, Cork in the second half of the 18th century. Specially the nonius is remarkable.

Country of manufacture

UK and Ireland

Category: Navigational instruments

Description

An historical interesting three mirror octant, made by Francis Fitton, Cork in the second half of the 18th century. Specially the nonius is remarkable.
The first octant was created by Headly in 1731. In Great-Britain and North-America it was called the Hadley’s quadrant to distinguish it from the Davis quadrant. Headly got in 1734 a patent for eleven years. Immediately after it came to an end other instrumentmakers started with making octants.
This octant is made of mahogany. The graduated scale is made in two parts with two scales and a Vernier nonius. The lower one runs from 0 (-5) to 90 (95) degrees and the upper, complementary, one from 90 to 0, just as it is with Davis Quadrants and early octants with transversal nonius. In the lower graduation every degree is divided in parts of 20 minutes, The Vernier nonius is divided in twenty equal parts. The accuracy of reading with the transversal nonius is one minute.
The lower horizon mirror and peepsight were used for backward observation. As the horizon just below the sun was invisible, in this way it was possible to use the opposite horizon. The instrument was used back to front. The observer had the sun in his back. The sunshades moved to the lower position.Both peepsights have two holes. The central ones for direct observation of the sun, the other ones, just outside the path of rays, could be used in stead of the sunshades to weaken the sunligth.
This beautiful instrument is complete and in a good condition, with three mirrors, two peep sights and two sunshades. On the backside three brass legs and the adjusing-screws.

 

Date: ca. 1770
HW: 45,5×38 cm   (18×15 in)
Radius (rotation axis till nonius): 39 cm   (15.4 in)
Signed: Made by Francis Fitton Cork
              For
Origin: Ireland
Condition: very well

 

Curious about more? Then switch to http://archipel-maritime.nl/

Ask the Dealer

Item enquiry

To enquire about this item, complete the form bellow to send a message to the Dealer

Enter Email
Confirm Email
Sending

Dealer information

NL ARCHIPEL - International Maritime Galery

Archipel – International Maritime Galery in the Netherlands, sets itself to maritime objects of before 1900. The managing director worked as officer with the mercantile marine and the Royal Navy. As curator he was connected to one of the university museums in the Netherlands. As seaman and curator he has a lot of knowledge of naval history.

Shipping information
Payment methods