The Aubrey holes are a ring of fifty-six (56) chalk pits at Stonehenge, named after the seventeenth-century antiquarian John Aubrey. They date to the earliest phases of Stonehenge in the late fourth and early third millennium BC. Despite decades of argument and analysis, their purpose is still unknown, although an astronomical role has often been suggested. Whilst visiting the monument in 1666, Aubrey noticed five circular cavities in the ground and noted them in his records. These features were ignored or not seen by the later antiquarians to investigate the site, and it was not until the 1920s during the work carried out by Colonel William Hawley that Hawley's assistant Robert Newall identified a ring of pits he named in honour of Aubrey and his early survey. The depressions seen by Aubrey himself are more likely to have been different features from those that now bear his name. Mike Pitts in a 1981 article in Nature pointed out that the holes had been backfilled thousands of years before Aubrey visited the site. The presence of later cremation burials and sarsen stone chips in the holes' upper fills supports this. That none of the other antiquarians who visited the site noticed any such holes implies that they were not permanent features either. Pitts argues that they were more likely to be the cavities left by features that had recently been removed. He has suggested that perhaps further megaliths stood at Stonehenge which occupied these other holes and are now lost. The Aubrey holes themselves Twenty-five of the holes were excavated by Hawley in 1920 and seven more in 1924. In 1950 Stuart Piggott and Richard Atkinson dug two more Aubrey Holes which brought the total excavated to thirty-five, including one that Richard Colt Hoare may have encountered whilst digging beneath the fallen Slaughter Stone (so named from its reddish coloration) in the early nineteenth century. It was found that the pits were an average of 0.76m deep and 1.06m in diameter. Twenty-five of the pits contained later cremation burials inserted into their upper fills along with long bone pins which may have secured leather or cloth bags used to hold the remains. Their presence makes Stonehenge Britain's oldest cremation cemetery. The pits appear to have been refilled with the freshly excavated chalk rubble soon after being dug as no weathering has been noted on the chalk sides of the pits. They