There is an interesting article in the essays presented to Stuart Piggott - Studies in Ancient Europe, this is one by Anne Ross - Shafts, pits,wells - Sanctuaries of the Belgic Britons. It is primarily a catalogue of finds excavated from the wells and shafts in a broad band from the Bristol Channel down to the south coast, though of course there is the Newstead, Roxburgshire fort with 15 pits excavated. These roman forts housed many different nationalities of the roman legions, and they of course brought there own religious gods and rituals to Britain.
Ritual pits have been excavated in the great Iron Age forts of Danebury and Cadbury Castle, showing that this ritual of communicating with the gods, or indeed the underworld was a native belief going back through time. Ross speculates that as some of these shafts are on hills that it was seen as a direct link down the the underworld, and it would be a wild speculation indeed to put forward that Silbury, with its trace of wood down the centre, may have in the past be seen as such a place by the celtic tribes.....
The things founds placed with care in some of these shafts, apart from cinerary urns, are skulls, both dog, horse and human; animal bones, bird bones, probably relating back to the religious aspects of particular birds; pottery and iron goods, and of course hazel nuts and hawthorn branches. The shafts themselves were often well made and lined, but it is well worth remembering that rubbish may have also been thrown down these shafts, and many a roman villa would testify to its overthrow, by the bodies of its former inhabitants tossed down its wells.
Ross examines these finds through a particularly celtic tradition that looks forward to the writing of the celtic monks as they wrote down the great legends of the Irish traditions, therefore her interpretation is tracing a religion long gone and only captured in a somewhat garbled form by monks, therefore if there is a raven beak found, one has only to look at Cu Chulainn dying with the raven of death perched on his shoulder to understand the significance of one small beak in a shaft.
Details of some local finds;
Cadbury Castle; Devon. A shaft, lined with puddled clay, earth gave way to sherds, ashes, fragments of bones, ornaments and beads; 20 metal bracelets and 4 of shale; at 30 ft. a bronze ring, perced jet button, glass and enamel buttons, horse teeth....etc
Caerwent. Monmouthshire. -Romano- British town; There were several wells in this settlement, but some seemed to be ritual; dog skulls were found in several places, as well as horse, a seated deity found in another with a collection of iron tools.
Danebury Hill; Hampshire. A cylindrical shaft filled with chalk and earth, containing large flints, bones and sherds. Ox bone and goat bone were also present, two other shafts at this side.
Heywood; Wiltshire. A well opened at Westbury Iron works, in 1879 contained a considerable quantity of broken pottery , a complete skull of Bos Longifrons, skull of a horse with a hole pierced in the cheek bone, and at the bottom 4 human skulls.
Jordan Hill; Somerset; A Romano-British temple; Well lined with clay, in which a layer of used stone tiles were laid edgeways. A rough cist of two oblong stones in which there were two urns, a broad iron sword, iron spearhead, knife and a steelyard;above this was a layer of thick stone tiles, on it a bed of ashes and charcoal. On this a double layer of stone tiles, arranged in pairs, between each pair was the skeleton on one bird together with a small roman coin. Beds of alternating ash and upper tiers of tiles, enclosing bird skeletons and coins, sixteen tiers in all, interrupted half way by another cist. The birds represented were raven, crow, buzzard and starling, all prognostic birds according to Ross. Hare bones were also found, hares are sacred animals in celtic mythology, Boudicca sacrificed one to Andraste before her battle with the Romans . http://www.stone-circles.org.uk/stone/jordan_hill.htm
Maiden Castle, Dorset; In 1868 seven pits were found, they contained animal bones, sherds of pottery and 'other pieces of hardware'
J.W.Brooke 1908– site of well immediately opposite Silbury Hill about 105 yards from the hedge on the south side…This well was dug by Cunningtons 1882 –WAM XXIX p.166. When Brookes uncovered this excavation, he found a mass of small stones of various sizes (backfill presumably), then at a depth of 5 feet came across a sarsen weighing about half ton, this sarsen must have stopped the earlier Cunnington Dig. Brookes removed it, roman finds were under it – perforated roofing tiles, square headed nails, iron bucket handle clip, moulded freestone corbelling, base of column. It took 6 days to reach the chalk bottom of the well 26 feet depth, encountered more largish sarsens…
note; sarsens found at the bottom of the two? towers of the churches here (a circle), Twyford is near Winchester.