¹De Vismes Kane, William F. M. "The Black Pig's Dyke: The Ancient Boundary Fortification of Uladh." Proceedings of the Royal Irish Academy. Section C: Archaeology, Celtic Studies, History, Linguistics, Literature 27 (1908-1909): 301-302.

²Condit, Tom. "Travelling Earthwork Arrives at Tara." Archaeology Ireland 7.4 (1993): 10-12.
The term "traveling earthwork" is also used, but "linear earthwork" seems to be more common.

³Other names for the Black Pigs' Dyke include: The Black Pigs Race, The Worm Ditch, The Worm's Cast, Duncla, and the Dane's Cast. ("Black Pigs Dyke – Regional Project." Roscommon County Council. Web. 02 June 2014. <http://goo.gl/DMhFj6>.) Some authors consider The Dorsey in Co. Armagh and The Dane’s Cast in Co. Down to be part of The Black Pig's Dyke.

⁴Davies, O. "The Black Pig's Dyke." Ulster Journal of Archaeology Third 18 (1955): 29-30.

⁵De Vismes Kane 303.
Kane presumed that the Dyke was intended to defend the Uladh from threats coming from the south due to fact that the rampart's slope was deeper to that direction. Later excavation added details regarding the greater height of the northern-most bank and ditch defenses. (Walsh, Aidan. "Excavation at the Black Pig's Dyke." Clogher Record 14.1 (1991): 9-26.)

⁶Braden, Una. "The Black Pig's Dyke." Personal interview. 30 June 1998.
In the interview Braden acknowledges that the warnings to children about the Black Pig's Dyke were "...probably another way for parents to say you better be home by twelve o'clock!"

⁷Rogers, R.S. "The Folklore of the Black Pig's Dyke." Ulster Folklife 3.1 (1957): 30-31.
The author notes, "This story has the authentic ring of myth and it is so well diffused throughout the length of the three frontiers in association with the rampart that I have taken it as the basic story."
The genesis of the legend may have been a narrative found in "The Tale of the Fate of the Children of Tuireann," one of the three "Sorrowful Tales of Erin," where Cian, Father of Lugh, changes himself into a Druidical pig and begins rooting up the earth to save himself from the three sons of Tuireann, who wish to kill him. Two of the sons of Tuireann, however, are magically transformed into hunting dogs, and they pursue the man-pig into a grove of trees, where the third brother flings a spear at him and kills him.
Here are the outlines of some variants to the basic story, taken from the Rogers article and from others listed below:
Occasionally it is the mother and not the father of the boy that changes the schoolmaster into the pig.
Sometimes the story is concluded with the prophecy that there will be war in the valley of the Black Pig. This is dealt within in some detail toward the conclusion of the essay.
Kane (1908) recorded this variation: "...the three sons of Tureann resolved to take revenge on the Druid [schoolteacher]; and on the occasion of his changing himself into a black pig pursued and killed him near Cnoc-Cian-mic-Cainte, sometimes called Killeen Hill, which is north of Dundalk; and Cian's grave was seen on the hill till about 1836, when a farmer named Dickie tore it down..."
Kane also recorded a version, near Granard, that inserts St. Patrick into the narrative: "When, however, the form of a black pig was assumed, St. Patrick took fresh courage, and, following the deep track or furrow that it left behind, succeeded at length in running it down at Granard, where the animal was killed, and the demon no more disturbed the countryside by his apparition."
Brian Sherry (1993) noted that "It was also widely believed in mid-Monaghan that before the end of the world The Black Pig would return and flatten the Dyke again."
Fionnuala Williams (1978) noted that: "Other methods of preventing the schoolmaster from changing himself back into human form were by closing or burning his book. An alternative to all these was to procure special hounds such as a pup of the first litter or a pure black bitch with no rib of white hair and simply lie in wait for the schoolmaster when he was out hunting with his pupils. He could also be shot with silver: pure black dogs and pure silver were believed to have the power to overcome supernatural beasts.
Our virtual-reality work in the area of Kiltycloger near where this story was collected was completed with the assistance of guidebook author Anthony Weir. Here is a photograph of three of the four members of the group: Anthony Weir, Malcomb Walker, and Robin Goldbaum (July 15 2013).

⁸De Vismes Kane 302.
Kane included both The Dorsey and The Dane's Cast in his assessment of The Black Pig's Dyke. He further claimed that John O'Donovan would have been inclined to agree with the more expansive map of the Dyke had the government allowed him to continue his field researches.

⁹De Vismes Kane 321.
To provide a dating framework for the Dyke, Kane largely relied on annalistic evidence: "But since the new frontier of Ulster was fixed during the reign of Tuathal Teachtmar, i.e. A.D. 130 160, the trench cannot have been made earlier ; and, on the other hand, this defensive boundary must have been put up before 332, when the destruction of Emania, and the overthrow of the Ultonian dynasty after 600 years' duration, were accomplished by the three Collas."

¹⁰The sources for the map animation were De Vismes Kane, W.F. "Additional Researches on the Black Pig's Dyke." Proceedings of the Royal Irish Academy. Section C: Archaeology, Celtic Studies, History, Linguistics, Literature 33 (1916-1917): Pl. XLVIII; and Walsh, Aidan. "Excavation at the Black Pig's Dyke." Clogher Record 14.1 (1991): Fig. 1.

¹¹Davies 29-31.
As evidence of how folklore is contaminated with published theories, the author states that the monument once called locally "The Duncla" assumed the name "Black Pig’s Race" by 1908 once it was so referenced in print.

¹²"Black Pig's Dyke." Wikipedia. Wikimedia Foundation, 24 May 2014. Web. 02 June 2014. <http://en.wikipedia.org/wiki/Black_Pig%27s_Dyke>

¹³De Vismes Kane 303-04.

¹⁴Lynch, Michael. "Dismay at Cavan County Council Quarry Decision." Indymedia Ireland RSS., 14 Sept. 2006. Web. 02 June 2014. <http://www.indymedia.ie/article/78401>.
The earlier article may be viewed here.

¹⁵Walsh, Aidan. "Excavation at the Black Pig's Dyke." Clogher Record 14.1 (1991): 15-26.
Not only was Walsh's work the first scientific excavation of the Black Pig's Dyke, it was also the first professional archaeological dig ever to take place in Co Monaghan, according to this newspaper story. As a part of the 2012-2017 Co Monaghan Heritage Plan, a new archeological exploration of the Dyke has been proposed. More details here.

¹⁶De Vismes Kane 306.

¹⁷Lett, H.W., and W.J. Fennell. "The Great Wall of Ulidia; Commonly Known as "The Dane's Cast", or "Gleann Na Muice Duibhe" Ulster Journal of Archaeology 3.1 (1896): 23-29.
In a subsequent article in the next issue of the journal the author speculated on the naming of such ancient monuments: "They saw about them remarkable features, and had to account for them; they heard about the Danes as terrible warriors, and so attributed these wonders to them; hence 'Danes' Forts,' "'the Dane's Cast,' and similarly, 'Giants' Graves,' 'Big Stones,' &c.–all names given by a people who knew nothing of the real authors or origin of the things they named."

¹⁸Walsh 10-12.

¹⁹De Vismes Kane, W.F. "Additional Researches on the Black Pig's Dyke." Proceedings of the Royal Irish Academy. Section C: Archaeology, Celtic Studies, History, Linguistics, Literature 33 (1916-1917): 544-45.
Kane acknowledges that manuscript sources and local folklore confirm the traditional site of the pillar stone outside the village of Rathiddy, in Co. Louth.

²⁰Fergusson, James. Rude Stone Monuments in All Countries Their Age and Uses. London: J. Murray, 1872. 294. Quoting W. Hackett.
Another source has further accounts of the natural features in folklore attributed to the Black Pig: "In Co. Monaghan, in the townland of Knocknacran, there is a field called 'Poll na muic' which has indentations said to have been made when the pig rolled there or when he lay there to rest. The field is three cornered and fields of an unusual shape like this tend to attract attention. In addition to having made indentations the Black Pig is also believed to have caused certain lakes and rivers." (Williams, Fionnuala. "The Black Pig's Dyke and Linear Earthworks." Emania: Bulletin of the Navan Research Group 3 (1978): 15-18.)

²¹Rogers 33.
The two locations where the author encountered the story of railway train as the Black Pig were Redhills and Ballinamore.

²²O'Kearney, Nicholas. The Prophecies of Ss. Columbkille, Maeltamlacht, Ultan, Seadhna, Coireall, Bearcan, Malacy, &tc, Dublin: John O'Daly, 1836. 7-8.
The author, whose text contains his own Colm Cille "prophecies" of dubious provenance, quotes the "Valley of the Black Pig" prophecy in order to decry its authenticity. This book may be read in its entirety here.

²³Hull, Eleanor. "The Black Pig of Kiltrustan." Folklore 29.3 (1918): 228-30.
The author asserts that "The re-appearance of the Black Pig at this moment appears to be by no means an accidental occurrence. The so-called Prophecy of St. Columcille, to which reference is made, is a long, ill-written, and quite recent prose tract which has been widely circulated and is firmly believed in the North of Ireland."

²⁴De Vismes Kane 322-28.

²⁵O'Donovan, John, Eugene O'Curry, Thomas O'Connor, and George Petrie. Letters Containing Information Relative to the Antiquities of Kildare II (v. 13). Collected during the Progress of the Ordnance Survey, 1834-41, Ed. Michael O'Flanaghan. Bray. 1927.

²⁶O'Kearney 13-16.
This book may be read in its entirety here.
"To hell or Connacht" was the phrase Oliver Cromwell used in describing where the native Irish Catholic population might relocate once their lands were confiscated by the English.
The author ascribes the origin of the false prophecies of St. Colm Cille thus: "The great compound of falsehood is embodied in a book of considerable size, purporting to be the genuine version of the Prophecies of St. Columbkille, which has been printed in Bow Street, Manchester, about 20 years ago. This pretended prophecy is an amalgamation of some few sentences found in the prophetic writings of the saint, a portion of the predictions attributed to Nixon, a considerable portion of localized pythonicism, and a suitable leaven of pagan traditionary lore. This book was pompously announced as the Prophecies of St. Columbkille — was eagerly bought, and no estimation can be formed of the amount of injury its perusal may have done to the people into whose hands it found its way. The original of this pseudo-prophecy, an old MS. copy of which has been once in our hands, purported to have been written, more probably compiled, by one Stephen Carpenter of Moynalty, county of Meath. But when this personage lived, and whether he pretended to have been a prophet himself, or a simple prophecy-monger, we are unable to ascertain at present. One thing, however, is certain, that he executed his task with a surprising cunning and tact, rarely to be found possessed by an ordinary country peasant. Those spurious prophecies have been, and are now a being published in different editions, varying in price from one halfpenny to a shilling!"
While O'Kearney sought to distance himself from the supposed Colm Cille prophecy of the massacre at The Valley of the Black Pig, he also, according to O'Donovan and others, was responsible for his own book of completely spurious Colm Cille prophecy. O'Donovan wrote: "Of all the silly prophecies attributed to St. Columbkille, THAT now published by O'Kearney is out and out the most absurd and the most barefacedly silly and impertinent! It is, in fact, a most daring fabrication in very bad Irish, by some very silly man, who has attempted to imitate ancient Irish poetical composition, without having sufficient skill to hide modern spelling and local idioms. The fabricator of the poem is either O'Kearney himself, or some very silly and ignorant person who has imposed upon him." (Madden, R.R. Exposure of Literary Frauds and Forgeries Concocted in Ireland, Spurious Predictions Designated Prophecies of St. Columbkille. Dublin: John P. Fowler, 1806. 2.)

²⁷Cambrensis, Giraldus. The Historical Works, Containing The Topography of Ireland and the History of the Conquest of Ireland, Tr. by Thomas Forrester; The Itinerary through Wales, and the Description of Wales, Tr. by Sir Richard Colt Hoare. Ed. Thomas Wright. London: George Bell & Sons, 1905. 279-80.
O'Donovan (December 12th 1837) attributes the spread of the false Colm Cille prophecy to Giraldus Cambrensis: "Cambrensis states that that the prophecies of Colbumbkille were preserved in books in his time and that the Irish people believed in them with the most implicit faith." (O'Donovan, John, Eugene O'Curry, Thomas O'Connor, and George Petrie. Letters Containing Information Relative to the Antiquities of Kildare II (v. 13). Collected during the Progress of the Ordnance Survey, 1834-41, Ed. Michael O'Flanaghan. Bray. 1927. 80.) However, in this online translation of Giraldus' Expugnatio Hibernica ("Conquest of Ireland") there is no mention of the Valley of the Black Pig in the prophecy attributed to St. Colm Cille. It may be that O'Donovan and others erred in identifying Giraldus" account of Colm Cille's prophecy with the Valley of the Black Pig.

²⁸Crawford, Henry Scott. "The Black Pig of Kiltrustan." The Journal of the Royal Society of Antiquaries of Ireland Sixth 8.1 (1918): 80-82.
Kiltrustan is near Strokestown, Co. Roscommon. The account of the sighting of the Black Pig also corresponds with some traditional fairy lore: "Crowds, full of awe, are visiting the place and the children of the parish are in a state of terror. Two men who cut a tree on an old rath or fort are ill, and many attribute their illness to the appearance of the pig."

²⁹Henderson, Lynda. "Review: At the Black Pig's Dyke." Theatre Ireland 30 (1993): 50-52.
This reviewer noted that this part of the Irish borderlands is hardly diluted "in its pagan sensibilities," citing the enduring popularity of "rural blood-sports like cock fighting and badger baiting [which] survived here after they had died out elsewhere."

³⁰Woods, Vincent. "At the Black Pig's Dyke." Far from the Land: New Irish Plays. Ed. John Fairleigh. London: Methuen Drama, 1998. 3.

³¹Yeats, W. B. The Wind among the Reeds. London: E. Mathews, 1899.
The author's notes on this poem are found in: Yeats, W. B. Later Poems. New York: Macmillan, 1924. 358.