Chichester Cross is a market cross – the building that symbolises the heart of the market square in my nearest town of Chichester, West Sussex.
The building is supported by 8 stone columns, like flying buttresses, and they are all exposed to the elements. What has any of this got to do with natural navigation?
Each buttress faces a slightly different way. And since there are 8 of them and they complete the circle, there is a 45 degrees difference in the aspect of each.
The stone is the same and the location is the same in each case and the only thing that changes is the aspect. This means we have a near perfect experiment for testing the importance of aspect on lichen and moss growth on stone in a town. And therefore how these can be used as a natural compass.
If you look at the photos below, you’ll notice how the stones facing south have fewer mosses and algae and more bright lichens.
There are also more mosses and algae on west-facing stone than east-facing as most of the rain-bearing winds come from the SW. So, for example, the SSW stone has more moss than the SSE one.
I’ll let the pictures do the talking from here. We move round 45 degrees anti-clockwise with each image starting at WSW (the aspect is written below each picture):