Equinoctial Ring Sundial

Astronomy

Accession Number: 2012.ast.17

Description:

Sundial mounted on large flat circular base with three adjustable knobs. In centre of base is a silvered compass with two glass bubble levels at right angles. Surrounding compass is brass ring marked on the inner circumference by days and months and graded on the outer circumference by 360 degrees, with each quadrant additionally marked “watch faster” and “watch slower”. Brass ring rotates on base, moved by brass key attached adjacent to “Feb.” marking. Mounted on rotating brass ring by two filigreed and floral legs is a brass main ring holding a double brass ring. Inner ring rotates outwards to right angle position from main ring. Inner ring has 24 hour markings (two sets of I-XII) on one side and on inner edge. On opposite side of the inner ring are lattitudes: “Naples 41, 51 / Paris 48, 50 / Copenhagen 55, 40 / Berlin 52, 30 / Dublin 55, 12 / Edinburgh 55, 58.” Passing through center of inner ring is flat rotating brass piece with sliding brass segment with tiny aperture. On one side are marked days and months, on the other, astronomical symbols. Outer ring graded on one side by 360 degrees, and marked on the other by additional cities and lattitudes: “Lisbon 38,45 / Constantinople 41,30 / Boston 42, 26 / Madrid 40,25 / Amsterdam 52,20 / Petersburgh 59, 59.” Attached to outer ring are two aligned apertures for alignment with the sun. Below main ring is small brass knob to rotate inner and outer brass double ring within main ring. Above main ring is a top piece with ring handle, maker’s inscription and small scale to match rotating gradation on outer section of double ring.

Alternative Name: Sundial

Primary Materials: Brass, glass, other metal (silver?)

Markings: On top piece: “Watkins & Smith, London”

Dimensions (cm):

Height = 38 x Width = 30 x Length = 30 (diameter = 30)

Function:

To find precise times using the sun. Sunlight coming through aperture on middle section falls on scale of hours. Instrument can be adjusted for latitude and date and oriented using the compass. Meridian point of the sun can also be determined through double aligned pinholes on attached to outer double ring.

Condition: Excellent

Associated Instruments:

Manufacturer: Watkins & Smith, London

Date of Manufacture: 1763

Provenance:

University of Toronto Department of Astronomy and Astrophysics – not used at U of T.

Donated to UTSIC: No

Historical Notes: UTMuSi entry ast500