The Light-Box: It was suggested that a 'light-box' feature had been discovered at the Crantit tomb. The suggestion of a discovery of a second light-box on the Orkneys is of extreme importance. Light-boxes are a megalithic construction feature that have so far only been recorded at three other sites in the UK, with two in Ireland (Newgrange and Carrowkeel - below) both having the same design, and the other in Maes Howe on the Orkneys in Scotland with a moveable light-box. The two known Irish examples: Newgrange (left), and Carrowkeel (right). At Maes Howe, the light of the setting solstice sun was restricted by the closing of a 'portal stone', placed into the side of the passage. In this way, at the right moment, the stone could be closed across the passage, and the light would only pass over the top (as at Newgrange). The same design feature is also present in the entrances of the three sub-chambers at Maes Howe, each of which also had a blocking-stone which closed most of the hole, but not all of it. (These stones now lay on the floor in front of the holes). (More about Maes Howe) The Crantit 'light-box'.   It was observed that 'a large stone spanning an area over the assumed position of the passage had a 'peculiar notch' in its upper surface. After the clay covering was removed, it was noted that this notch allowed light into the rear chamber, and that the notch was aligned on the horizon. Could this notch be a way through which the light of the rising sun would shine and illuminate the darkened chamber at a particular time of the year? As the entrance passage faces SE it could possibly be winter solstice.   Extract from Field-notes: 'If you look at the above image you will see the passage blocking slabs (the two thinner stones at the bottom of the picture) come right up to the large notched cross slab (the notch is directly below the scale). It was previously thought that this large slab was the main passage lintel, but I doubt this very much. This is mainly because it seems too high; the passages in other chambered cairns are much lower than the main chamber and I suspect that here the passage lintel is further back and lower. Now, this would mean that the passage 'blocking' rises above the actual passage opening. Consequently, the blocking must have been undertaken from the inside'. 'This suggests one of two possibilities, first, someone during the Neolithic was actually shut inside the chamber, or more likely access was gained through the roof. If the latter is correct then it suggests the clay covering was not there during the use of the chambered cairn. This would allow fairly easy access through the roof slabs. More importantly, the absence of the clay covering would allow sunlight to shine through the notched stone into the chamber'. The orientation of the passage and the fact that the notched stone appears to be set above the height of the passage which was blocked, combine to suggest that this particular construction feature was probably deliberate in design. The act of blocking the passage gives the notched stone its purpose, as it becomes the only means of sunlight entering the chamber. The uniqueness of this 'light-box' is its placement in such a small monument, as it has only before been seen in constructions on a 'civil' scale. (More about the Crantit Dig. 1998: http://www.orkneydigs.org.uk/crantitdig/index.html)   (More about light-boxes)