We read a sundial from the outside, and therefore the gnomon is in the centre and the numerals are on the outside. If, however, we stood in the centre of a vast dial, a series of gnomons would be required to replace the numerals. This is the stone circle. As a primitive example, the Cadster circle will suffice for its class. When the circle was constructed, the “pointer,” instead of being a point to the west of south as it is now, a variation owing to the obliquity of the earth’s axis, stood exactly due south; therefore the seer, sighting from the point of the central monolith, knew that when the sun was directly over it the time was mid-day—the greater distance assisting the accuracy. Similarly the east stone is now a point to the southward, so when the sun rose over the horizon in line with it and the central monolith, it was the May festival, and so on for every phase of the sun. Obviously, the northern stones would be useless for this purpose; but the object of the vallum was to enable the line of sight to be also taken across the circle from the outside, and over _any_ stone and the central dial, or over any two stones, thus subdividing the then equivalent to the hours and the months. The slope of the vallum lent itself to any level required by the observer whilst taking his observations, and the entrances enabled the people to pass through the circle to make their obeisance, whilst the arch-astrologer stood by the central monolith giving his instructions and advice. To them his simple predictions would seem to be the greatest of miracles. As the “pointer” is not always in a southerly or northerly position, for the latter would serve the same purpose if the point of observation were transposed, it follows that various monuments were dedicated to or were specially required for various seasons or times; the winter or summer solstice and the spring or autumn equinox being the most popular. The points of the stones would be accurately notched or, perhaps, surmounted with a wooden stile or pierced disc. In the larger circles the same system would be carried out with greater accuracy. The ditch and vallum enabled the sights to be taken from either the foot or the top of the stones, and the mound would, if required, itself form the horizon. The ditch was certainly not for any processional ceremony, for that at Arbor Low was found to be broken across by faces of natural rock three or four feet in height; but the curved causeway leading towards the great pointer, Gib Hill, may have served that purpose when the seer left the circle to take his observations, and probably to invoke the rising sun from the mound. The central dolmen would be the inner temple of the priest, and the greater distance of the circle of stones would increase the accuracy of his observations.