Exhibit № 34: John Rowley, London. Circa 1715

15¼  inches

The Time Museum, Rockford, Illinois, USA, inventory no.2680;

Sotheby’s Olympia, 30 Oct. 2002, lot 23, sold for £32,077;

John C Taylor Collection, no.106.

G Clifton, Directory of British Scientific Instrument Makers, 1550-1851, London, 1995, 238-9

JR Milburn, ‘John Rowley’s Ginnery Instruments’, Bulletin of the Scientific Instrument Society, 32, 1992, p.3-5

435mm

1990s, The Time Museum, Rockford, Illinois, USA

Signed I Rowley London on the outer meridian ring and similarly on the bridge, the meridian ring calibrated with a degree scale in four quadrants reading to 30 degrees from the equator, its reverse with a ‘nautical ring’ scale for measuring altitudes, the equinoctial ring engraved on its outer and inner faces with an hour scale reading to minutes (I-XII-II), the bridge engraved to one side with an ecliptic and declination scale, and to the other side with a month scale (0 degrees Aries =m 11 March). Around the meridian is a semi-circular ring in two parts joined by a screw passing through the raised eyes attached to the ring; to adjust it against the degree scale for latitude the screw is slackened, unclamping the two semi-circles, so that the suspension piece mount may by slid along. The cursor may be clamped in position by tightening two screws.

This ring dial is of exceptional size for its type. It is considerably larger than the next smaller, a 14½in. ring dial by John Evans, Bishopsgate, London (Sotheby’s Olympia , 20 Sept. 2001, lot 38), and is second in size only to an unsigned 18in ring dial (Sotheby’s Olympia, 30 May 2002, lot 33)