A Barker Patent Combined Prismatic Compass and Clinometer, also known as an 'Angle of Sight Instrument'. This instrument was patented by Francis Barker & Son in 1881, and dates from 1881-c.1895. Although there are no maker's marks, this is a Barker design that was usually supplied unsigned to scientific instrument retailers such as Louis Casella (1812-1897), who would often add their own company details to the lid or compass card.
This instrument has a cut-out aluminium ring compass card, to be read via the prism. Above this is positioned a white clinometer card, marked with various scales and inscribed 'Inches Per Yard', and with the Barker patent no. 1926 at the centre. Fixed above the clinometer card is a cut-out upper layer with an aperture for reading the compass and clinometer cards, marked at the edge with the serial no. 2608. The brass hunter case has an 'Oxydised' or bronzed finish, circular viewing window with lubber line to the lid, side mounted prism, clinometer release button, manual brake, and a tripod mounting point to the base. A small section of the lower part of the brass case and lid have been flattened to provide a stable surface or ‘foot’ when placed vertically on a surface for use as a clinometer.
William Ford Stanley described this instrument in his book Surveying And Levelling Instruments (1895) as 'Barker’s Combined Prismatic Compass and Clinometer', 1881 Patent No. 1926. Stanley stated that: 'A part of the clinometer card is cut away so as to enable the compass card to be read beneath. This cut-away part is held by a stop to a position out of the field of the prism when the instrument is to be used as a prismatic compass. When the stop is released and the instrument is held with its face vertical, the pendulous clinometer card comes into view'.
Further information on Barker Compass Clinometers can be found at trademarklondon.com in the PDF version of Paul Crespel's book Trade Mark London, and examples of the Casella retailed versions can be seen at compassmuseum.com.
Francis Barker & Son: were established in London in 1848, as a maker of compasses and scientific instruments. Francis Barker produced a very wide range of compass designs over the years, supplying major retailers such as Negretti & Zambra, J. Lizars, C. W. Dixey, Dollond, Casella, and many others. The company prospered until 1932, when it was taken over and became F. Barker & Son (1932). After WW2 the company changed hands several times and Barker compasses are now manufactured by Pyser Optics at Edenbridge in Kent. They continue to produce the renowned Barker M-73, widely acknowledged to be the world's finest prismatic compass.
Condition:
The compass clinometer is in very good condition, full working order and finds North very well. The clinometer is in full working order. The original 'Oxydised' or bronzed finish of the case has worn away in places. The glass, prism, and both compass and clinometer cards are in very good condition.
Dimensions : 70mm diameter (100mm inc. prism), 25mm depth
