Horizontal pedestal dial for latitude 53° North. The bronze, circular dial-plate has an hour-circle and a minute-circle round its outer edge. Just inside the hour-circle, midday is marked for various cities by name and with a 'XII' at the appropriate spot, ranging from 'Mexico' in the west to 'Peking' in the east. Inside this is a table for the Equation of Time accompanied with instructions for its use. In the centre of the dial-plate is a wind-ring, marked by English initials. The pierced gnomon has a scrolled vertical support and a hole that supported a plumb bob (now missing). On it is southern edge is engraved, 'UMBRA NEC UNDA MANET' [Neither shadow nor wave endures]. Within the hour-circle is the maker's signature, 'R. GLYNNE FECIT 1753'.

Such a dial (similar to those still found in gardens today) must be set up so that the noon line lies along the meridian with the hours arranged symmetrically on either side. It was made for 'WILLIAM EDWARDS OF IOUNS.TOWN ESQr', which is probably Johnstown, the small town Southwest of Wrexham in the Welsh borders. The dial is marked with various cities around the world so that when the shadow of the gnomon falls on the mark for midday in these places, the concurrent time in London can be found. The longitudes given on the dial-plate for some of the cities are not consistent with current values. Some, such as 'Copenhagen' and 'Constantinople' are several degrees different from the modern values, but others such as 'Bantam' and 'Peking' are accurate to the nearest degree. These inconsistencies suggest that London was probably taken as zero longitude but that there were inaccuracies in the engraving of the plate.

For more information regarding this dial please refer to the OUP & NMM catalogue, 'Sundials at Greenwich'.