As we head towards the end of the year, the passage of time crops up in many conversations; ‘where has the year gone!’, ‘I have no time to get everything done for Christmas’, ‘time is just flying by’. We take it for granted that we can look at our watches or phones and know exactly what the time is and how long is left in the day for those vital chores.
Over many hundreds of years the way to mark time passing has become more sophisticated, from water clocks and candles to digital and perpetual clocks. Early time devices, which relied on water, fire or the sun, were on the whole not very portable, but with all technology someone is always working on making things smaller!
During the excavations at Corfe Castle in 1989 we uncovered a curious flat bronze disc with strange symbols engraved on one side.
A bronze disc with engraved decoration and roman numerals
The symbols were roman numerals, but not like a clock we would recognise, from one to twelve, but four to twelve and one to eight. There were two raised sockets, one on the upper flat edge and one on a decorated bar that ran from one side to the other one third of the way down the inner edge. What we had found was part of a pocket sundial.
A drawing of the sundial showing the decoration and sequence of roman numerals
There would have been a ‘gnomon’, the usually triangular shaped part that casts the shadow, between the two raised sockets, and the ring would have been set above a compass. You would need to know were north was so that the sundial could be orientated north. You would also need to know what latitude were you were as each dial would have been made for use at different latitudes.
An example of a complete engraved brass pocket compass and sundial. Part of the NT collection from Snowshill Manor, Glos.
We contacted the British Sundial Society (sundialsoc.org.uk) for help to identify our dial. They told us that “the part of the pocket dial you have appears to be the top ‘lid’ of a portable dial typical of many from the late 18th early 19th century. The bottom part of the dial would have contained a magnetic compass in order to orientate the dial so that the gnomon faced north. The spacing of the hour lines around the ring indicate that the dial was made for the latitude of about 51 degrees and this would also have been the angle of the gnomon”
The 51 degree latitude line is the one that passes through Southampton
Corfe Castle is where the ‘t’ in Bournemouth is on the map, just to the south of latitude 51 degrees. We need to make a gnomon and take the dial, and a compass, to Corfe Castle to see if it works, something we have never done! I will try and remember to post about our test when we have had chance to do the experiment. It’s catching a sunny day that may hold things up!
The diameter of the dial is 460mm
Archaeology National Trust SW 