Images(22)

Left: pelorus with sighting vanes. Right: soft iron rod "5" mounted vertically on deck.

The …

Beall's compass deviascope

Date1900-1915

Inventory NumberDW0141a-p

ClassificationDeviascope

Subject

Maker Henry Hughes & Son, Ltd. 1903 - 1947

User Institute of Geographical Exploration 1929 - 1952

Cultural Region

Place of Origin

Dimensionsassembled deviascope: 103 x 102.5 x 54 cm (40 9/16 x 40 3/8 x 21 1/4 in.)
storage box: 33 x 34 x 26.5 cm (13 x 13 3/8 x 10 7/16 in.)

Material

Accessoriesinstruction manual for instrument is in box of disassembled parts.

Bibliography

Handbook to Beall's Compass Deviascope

DescriptionThe compass deviascope consists of a ship-shaped platform (carrying a binnacle, small pelorus, and other accessories) mounted on a yoke that rotates in the center of large pelorus, which in turn is fastened to an ebonized rectangular pedestal.

The major parts are stored separately and identified as follows:

DW0141a--the ship-shaped platform attached to a yoke that turns above a large pelorus.

DW0141b--the rectangular pedestal of ebonized wood.

DW0141c--the magnetic compass and binnacle. This consists of:

part 1--binnacle frame with clinometer scale, supports for "cannon" balls, and tube for housing a vertical magnet.
part 2--compass bowl with pointer for clinometer
part 3--circular magnetized frame and pivot for floating compass card
part 4--compass card with printed wind rose
part 5--glass cover for compass
part 6--sighting vanes
part 7--two "cannon" balls

DW0141d--small, deck mounted pelorus:

part 1--pedestal with printed compass card
part 2--sighting vanes

DW0141e--soft iron rod (labelled "5") in collar to be deck-mounted behind the compass

DW0141f--pair of soft iron, hollow cylinders (labelled "3") to be mounted below the deck.

DW0141g--alternate pair of soft iron, hollow cylinders (labelled "4")

DW0141h--hollow, soft iron rod with flange on base to be deck-mounted in front of the compass. (missing)

DW0141i--four small bar magnets, each with a fin that can be inserted into a groove on the ship deck.

DW0141j--compass card on stand for vibrating needle experiments.

[Please see the separate descriptions and photographs of these parts for details.]

Signedon clinometer scale: BEALES DEVIASCOPE / H. HUGHES AND SON LTD. / LONDON

Inscribedon back of clinometer scale (upside down): 953A

Curatorial RemarksThe entire deviascope is stored in four parts: - the deck and large pelorus (DW0141a) - the pedestal (DW0141b) - the long iron rods "3", "4" and "5" (DW0141e,f,g) - a cardboard box containing the binnacle parts -including quadrantal spheres- (DW0141c), small pelorus (DW0141d), short iron rods "6" (DW0141h), small magnets (DW0141i,j), compass card for vibrating needle experiments (DW0141k), and the parts that have not been confirmed as part of the deviascope (DW0141l,m,n,o).

FunctionThis is a device that simulates the magnetic forces to which a compass is subjected on board an iron ship and shows how to cancel them out. It was used not just for illustrational purposes, but also for training navigators in using compasses onboard ships. They were questioned with it before getting their degrees and working on an actual ship. It was a standard examination tool for many seafaring-related institutions in the British Empire and several other countries.

The model consists of a pedestal that can hold the platform above in different angles and inclinations by a metallic arm. The platform represents the ship and has the compass close to its center. The many groves that extend radially from the compass are the places where one can position specially designed magnets to simulate or counterbalance the permanent magnetization of the ship. The small holder below the compass, the iron globes, and the square apertures below the platform with iron cylinders in it are all used to represent different components of the disturbances that a compass would be exposed to at sea.

An accessory called the pelorus or "dumb card," which stands behind the compass, is used to indicate the true direction of the ship.

The illustrator would place several magnets and iron objects in particular grooves and holders and show the effects that this had on the compass needle. An examiner would present a previously prepared arrangement to a student that would be required to ascertain the direction of the ship, which could include changing the direction and inclination of the platform (the ship) during the examination.

ProvenanceDavid Wheatland purchased from the Harvard Institute of Geographical Exploration, 1957.

Historical AttributesThe compass deviascope was first exhibited in 1886 and won a gold medal at the Liverpool Exhibition. It was a popular training tool for navigators until the early 20th century. This example was purchased by David P. Wheatland in 1957 from the Institute of Geographic Exploration, Harvard.