Scarce Barker Combined Altitude Instrument & Prismatic Compass Patent No 1926

A rare antique combined prismatic compass and clinometer serial no. 3417 by Francis Barker, London for Frost & Shipham, Perth, Wa c.1900. Combined compass clinometer having lower 2” diameter green Singer patent style compass card displaying 0°-360° divided to 1°, mirror-reversed so as to be read via prism, cardinals and intercardinals, star and lyre indicating North. The verso balanced with sealing wax. Second middle 2” diameter white card with outer mirror-reversed scale 0°-180°-0°, and middle scale 90°-0°-90°, both divided to 1°, and inner non-linear scale 48-0-48, marked ”Inches Per Yard.” Further marked “Patent No. 1926” to centre. Fixed upper silvered layer with aperture for reading cards, marked “Made by F. Barker & Son, London for Frost & Shipham, Perth, W.A.” and with serial no. “3417.” Flat glass with lubber line held within a lacquered brass bezel. All contained within an oxidised brass hunter case, glazed circular viewing port with lubber line to lid, side mounted sliding prism, clinometer release button, and momentary brake, large suspension ring to verso. Condition: Very original and in good working condition, the green compass card crisp, the white clinometer card with signs of ageing. Both cards swinging freely, the compass finding north easily. The upper silvered layer with a few light marks, the glass undamaged, the brass hunter case retaining much of its original oxidised finish. The leather carry case in very good condition, the stitching intact, with only a few minor marks. Comments: William Ford Stanley, in ‘Stanley’s Surveying & Levelling Instruments’ of 1890, refers to this as “Barker’s Combined Prismatic Compass & Clinometer.” Barker’s patent no. 1926 was registered in 1881, and although these combined compass clinometers instrument was most usually found in the relatively common 3” and 4” diameter sizes, see the page from the Francis Barker Catalogue of 1919, the earlier Francis Barker Catalogue of 1909 refers to a 2” version also being available. This is such an example, with probably just a very few made to special order over the period 1890-1910. The prismatic compass, a Hutchinson’s type, is combined with a clinometer, the white clinometer card mounted over the green compass card on a pin axis. A part of the clinometer card is cut away to enable the compass card to be read beneath. This cut-away is held by a stop to a position out of the field of the prism when the instrument is to be used as a compass. The larger Hutchinson’s type prismatic compasses have a glazed opening in the outer case near the prism that affords sufficient light to read the compass card easily. This smaller compass clinometer, with its hunter style case, has a fixed ‘mask’ layer with an aperture for viewing the cards. The prism itself slides up and down, and the reading taken by looking through the prism towards the sighting vane on the opposite side. When used as a clinometer the weighted clinometer card is released by pulling the release button at the top. Held vertically it is sighted in the same way as when used as a compass and the clinometer card read through the prism, which can be raised to suit. It can also be used to measure the slope of a surface, either in degrees or inches per yard. The lower part of the brass case and lid have been flattened to provide a stable surface or ‘foot’ when using as a clinometer. Frost & Shipham was a Perth, Western Australia- based optician and supplier of scientific instruments, who, in the The Western Australian newspaper of 17 August 1910, advertised that “they have a very large assortment of compasses, some of which have special improvements.” We have seen just one other of this smaller diameter Francis Barker combined compass clinometer – an instrument retailed by Casella, and carrying serial no. 1909 is displayed on the CompassMuseum.com website. Scarce, in good working condition, and definitely one for the collector!