Functions of Poseidon
Poseidon (Neptune) forms a triad, a trinity with Zeus (Jupiter) and Hades (Pluto). De Grave states (II, 148) that at the division of the empire of their father Saturn, the task of regulating maritime affairs had been assigned to Neptune. Apart from fishing, the main thing was to monitor maritime or hydraulic works, which were necessary to protect the land from the rage of the sea and to provide comfortable and safe ports, which is why one of Poseidon's nicknames in Greek was Asfaleios (= Security Deliverer). The most important maritime activities consist of the construction of piers, harbour heads in the sea, which were built with a triple row of wooden posts, braided together with brushwood and reinforced with stones. These three rows of "teeth" are symbolically depicted with the trident, the attribute of Neptune. Of course, a wall of earth or sand is not enough to withstand the force of the sea; wooden posts and stones formed a barrier, a "tuin" or "dune". Just as Sithium (St.Omer) is derived from si-tuin (-sea dune), a barrier in the sea, Neptune can be traced to nep-tuin (=squeezing dune), a barrier that "squeezes" or pushes away (from old-Dutch 'tuinen'). Compare this to the place name Sidon, a Greekification of Sithium, where -don means "tuin, barrier". Poseidon is, therefore, a Greekification of Neptune, in which posei- is associated with the Greek piezei (-squeeze, suppress) and -don with dune so that the name Poseidon also means "pressure barrier".
Another etymology of Neptune is from neap (dead water) and duining (spring tide), making him the god of the tides, especially that of extremely low and extremely high water.
These piers with their masses of stones gave Pindaros reason to call Poseidon Petraios (-Rocky): the god of the masses of stone.1
The function of Poseidon's son Triton is even more specific: he breaks the waves and stops the storms with the help of a shell. Also in the name Triton is tri (-three), symbolic of the three-part harbour piers. The port of Cadiz is called Forkus, derived from fork, with which the two piers in the sea are indicated (see Introduction Ithaka).

Forkus Harbour, Cadiz (=Ithaka), left leg now under water

When Poseidon, the Earth-shaker, breaks open Earth with his trident, it is not so much to cause earthquakes, but it should be taken allegorically as breaking open Earth through ports and harbours, enabling communication and shipping.

Another attribute of Poseidon is the dolphin, symbol of fishing, as indicated by Homeros in the story about Skulla in 12.93 ff:

So she (Skulla) extends her heads from that menacing chasm .
While fishing she eagerly scans the rocky coast: she catches
dogs, dolphins and sometimes larger creatures, that
moaning Amfitrite breeds in countless numbers.

The big sea creatures that Skulla catches are breeded by Amfitrite, Poseidon's wife and Triton's mother. Her name amfitrite is also related to the harbour heads, as tri points to the trident of the piers and amfi means "shelter all around": the sea space enclosed by harbour heads.2
This goddess is also connected to the Atlantic world, because she flees to Atlas, when Neptune wants her. He still gets her with the help of a dolphin, which is then elevated to a constellation (also called Triton). An explanation for this myth is that Neptune's marriage to the sea goddess indicates the development of seafaring, such as that of Herakles with Hebe (see Introduction Herakles, H.O). The dolphin's help points to the significance of fishing and fishermen, always venturing farther from home across the open ocean and discovering trade routes. The zodiac sign Dolphin, therefore, opens the fishing season.

The Earthshaker
Despite his role as protector of ports, fisheries and seafaring, Poseidon can rage with ferocity on all waters of the world. In 1.68, he is called Gaiéochos which is usually translated as "Earthshaker". However, the word means "Earth-embracing". The god that actually encompasses the whole earth with his ocean water is Okeanos. However, Poseidon makes use of this element of water and can, therefore, be found all around the earth, where he can cause major storms and seismic movements at sea that can cause tsunamis. For example, on the beach of Lagos (= Lakedaimon, Portugal) there is a warning sign for possible tsunamis. A possible reference to a tsunami in ancient times can be found in 11,235 ff, which talks about a mythological figure Turo who was in love with Enipeus. The fragment is discussed in detail in the Introduction Fenicians. The myth is reminiscent of a bygone era when the island of Tur and the coastal area would have been flooded by a tsunami (= Poseidon with the curled purple wave) and would have largely disappeared into the sea. In order to avert the danger of such tsunamis,  Bronze Age people would give him sacrifices of bulls and rams, both of which were used as a symbol for the tidal movements. Homeros gives an example of this sacrifice in 3.4 ff.

The residents just were sacrificing pitch-black bulls
on the seashore to the Earth-Shaker, the god with blue-black hair.
There were nine stands, each with five hundred people;
nine bulls were waiting in front of each stand.

Nestor slaughters 81 bulls on the beach of southern Spain (Pulos-Palos), see Introduction Pulos.
Also in 3,179, there is a bull sacrifice to Poseidon by Nestor and Diomedes, after they have safely crossed the Gulf of Biscay and landed in Northern Spain. From this, it can be concluded that the travel advice that both gentlemen asked a god in Lesbos, which has been identified as the Gulf of Morbihan, has been given by Poseidon, who was thought to make predictions by means of tidal movements and whose temple was usually close to the sea, see Introduction Lesbos. Weather forecasts were and still are vital for shipping. Proteus, subordinate to Poseidon, the master of oceanic currents, symbolizes, for example, the predictive power of the Seine flood. For his metamorphoses and the Proteus prediction method, see Introduction Aiguptos.

Poseidon's ferocious primal power is also reflected in his savage son by the nymph Thoösa: the one-eyed Cyclops Polufemos, with whom Odysseus must fight in book 9. The father of Thoösa is Forkus, after whom the fork-shaped port of Ithaka is named where Odysseus is landed by the Faiakans, see above. According to Wilkens (p.210), one eye in the middle of the forehead was a token of impulsivity, 'as his behaviour was determined by the subconscious, much like a volcano draws fire from the bowls of the earth. The Cyclops therefore stood for the uncontrollable physical strength as opposed to the subtle forces of the mind.'  See also Introduction Cyclopes.
Another example of Poseidon's ferocious power is the following fragment in which the walls of the Achaian ship's camp are swept away in one great flood from all the rivers in the plain of the Cam:

... then Poseidon and Apollo planned to destroy the rampart,
harnessing the hydropower of all the rivers
that flow seaward from Ida's mountains ...........
......... The Earthshaker himself, the trident in hand,
took the lead and carried away on the waves the trunks and stones of
all foundations the Achaians had built with hard work and
smoothed everything alongside the strong current of the Hellespont. (XII, 15 ff.)

Fortunately Odysseus enjoyed the protection of Athene, the goddess of wisdom, who saved him on several occasions against this primal force' (Wilkens p.414).

Poseidon's residence
According to 5,381, Poseidon has sea horses, with which he crosses to Aigai from Iberia, from where he had seen Odysseus floating on his raft. A second mention of Aigai is found in XIII, 21, which tells how Poseidon reaches his glorious 'dôme' (domata) in the depths of the bay in three or four steps from Samos in Thrace. "It is a beautiful golden water palace built for eternity."


This Samos in Thrace is situated by Wilkens (p.99, see map) in the hills of Sandringham east of the Wash above King's Lynn (map nr 20). According to him, King's Lynn is Lyrnessos mentioned by Homeros. This name is derived from Lyrnesos - "Lyr Island", which was called Linne (from Lyrn-eye?) in the Middle Ages and since King Henry VIII King's Lynn. It is striking that the Celtic name for Poseidon is Llyr! This city was destroyed by Achilles during a raid (XX, 92) in which he captured his sweetheart Briseïs.

Cailleux (PH these 13) states the name Aigai might be traced to agua, aqua (-water) and that we should look for his cave-dwelling at the mouth of the Humber (map: above Imbros) in England. Homeros calls this place a "wide bosom" where Thetis also has her caves (Il.24,80), which corresponds to the geography of the Humber. There he feeds his horses with ambrosia, an indication that we should see Poseidon as an ancient, dead cave saint. See also chapter Hermes above. Amber was and still is found on this coast (PH 340). Cailleux's explanation makes sense since Poseidon can get from King's Lynn to the mouth of the Humber in a few divine steps. In the absence of further indications, we cannot say more with any certainty about the location of Aigai.
However, Neptune's residence in Britain is also indicated by the names of Neptune's sons: Albion and Borgion, the first of which gave his name to Britain and the second to Northern Brittany, which was called Vorgion by Caesar. When Herakles went to war against these two giants, Zeus helped him by throwing huge stones at them, which can still be seen today on the former mythical battlefield: they are the countless dolmens and menhirs on both sides of the Channel (PH 306)!

The punishing Poseidon
In the Odyssey, we usually see Poseidon acting as a punishing god. In this way, he punishes the brutality of Ajax, the crime of Odysseus and the Faiakans.

-The story of Ajax's return and fall (3,499 ff) has been extensively discussed in the Introduction Channel Route. His boast was punished by Poseidon covering him under a huge piece broken off the island of Sark, now called Breqnau.

-The story of Poseidon's revenge on the Faiakans for bringing Odysseus back to Ithaka is extensively told in the Introduction Scheria. The Puerto de Naos in Lanzarote recalls the fact that after returning this fast ship was turned into a rock by Poseidon just in front of the city (13,159 ff). This punishment by Poseidon is remarkable, because like other gods he has a warm heart for the Faiakans elsewhere. Queen Aréte is, according to the family tree of 7.56, even a great-granddaughter of Poseidon and the god was honoured on the island with a large stone temple on a city square near the harbors, standing on a floor of heavy stones (6,266). In Poseidon's view, however, the Faiakans had misused the possibilities of shipping he offered by transporting the "criminal" Odysseus.

-Of the two shipwrecks that Odysseus suffered, the first was the result of the misdeeds of his men in Thrinakia where they attacked the cattle of Helios, see Introduction Thrinakia. However, the second shipwreck with its raft is entirely due to Poseidon. For Odysseus is, before his final initiation, a "good-for-nothing weakling", as he is called by the Cyclops Polufemos (9,515 ff.): "Now a puny good-for-nothing weakling blinds my eye, after plying me with wine." He is an idiot, an uninitiated, who even behaves arrogantly towards Poseidon in 9,525, claiming that even Poseidon couldn't heal Polufemos' eye! This overconfident attitude means that Zeus does not care about the sacrifices he makes in 9,552 and also stirs up Poseidon's anger, which will damage him later. In this way, Odysseus remains a "Nobody", an uninitiated one, who is not sufficiently rational but is still too much influenced by emotions and still too much bound to matter.

In 11,119 Teiresias predicts in the underworld how Poseidon's anger will eventually end. As a fine for blinding the Cyclops, Odysseus must make a pilgrimage to the interior of Spain, where people have no knowledge of the sea, sea salt and seafaring. There he will meet another traveller who calls his oar a flail. Then, as a sacrifice to Poseidon, he must slaughter a ram, a bull and a boar that pounces on the sows. This entire passage is a great mystery to the commentators. Cailleux (PA 326) identifies this inland site with the area where three major Spanish rivers originate, the names of which are indicated by the sacrificial animals. The ram is the Car of Xucar (car = ram in Fen., Hebr.), the bull is the Turia (-toro Sp.), also called the Quadalaviar (= aqua dal varre -'water of the bull '), and the boar and the sows represent the Tagus, which is a tidal river (bor, boar is  flood"; taya is  swine"). The boar that pounces on the sows is, therefore, the flood that penetrates deep into the Tagus.
A dolmen was usually erected in such mountain areas, with neighbouring peoples offering sacrifices and organizing orgies. Such a boundary stone is called piedra hita (-black stone) or in Saxon: paelsteen (pole stone)3. In such an area, ships were manually lifted or rolled overland from one river to another, as the Argo was transported by the Argonauts from the Po to the Rhône. In the area referred to here is the town of Arcabriga, which indicates this transport. Arca (= argo) is a transportable boat and briga is  berg"(-mountain), so Arcabriga means  Boat Mountain".4 This region was called Edetania in Roman times which could mean Hitaland (=Paalsteenland, pole stone land). However, ede (-hita = Ida) also contains the Gallo-Germanic root  eed" (-oath) with which the adjoining peoples confirmed their mutual treaties and contracts. The oar that Odysseus has to put in the ground symbolizes this barrier. It looks somewhat like a flail that also has a flat end.
The 'other traveller' or pilgrim may be related to the legend of the eternal traveller Achaverus, whose name can be traced to ach (-brother) and yver (-religious). It is a religious brother or mendicant, as Odysseus himself is later turned into a mendicant by Athena in Ithaca. Ulysses may have given his name to the people who live just north of this area: the Lusones.
Slaughtering the above mentioned sacrificial animals in honour of Poseidon is, therefore, the final atonement for injuring Poseidon's son, the Cyclops. Teiresias' prophecy about the death of Odysseus (11,134 and 23,268 ff.) points to the end of Poseidon's revenge: 'Death will appear from the sea for yourself: it will be a very gentle death, taking you when you are bowed with comfortable old age.'

We conclude with Wilkens that Poseidon  with the dark hair" was the god of the ocean with its tides, dark colour and enormous waves. Although our Atlantic authors have different views on the origin, functions and etymology of Poseidon/Neptune, it is clear, particularly through the combination of Poseidon with Okeanos we so often find in Homeros' text, that we are dealing with an Atlantic and oceanic deity. There is no doubt that in Bronze Age Poseidon was already worshipped on the Atlantic coasts, such as in Zeeland where he is depicted on many Nehalennia altars; on the south coast of Iberia, where he was offered sacrifices to prevent tsunamis; on the Canary Islands with the Faycans (Faiakans), where he had a temple; in England, where he watched the battles of the Trojan War and had his dôme at the Humber estuary; and in France, where he had a temple near Carnac. His actions are positive in promoting fisheries and seafaring, but they can also be negative when people make him angry because of their misdeeds, arrogance or indifference. Then he causes shipwreck and tsunamis.

1.Pind. Pyth. 4, 246, with the Scholiast.
2. Other etymologies of Amfitrite are: amfi and trit - "sea all around" or amfi-tread - "tread on both sides", see Introduction Cornwall,Thrinakia.
3. Compare the name Palestine, between the Jordan and the Orontes: derived from Paalsteen (-Pole stone)
4. See Introduction Fokaia.        

Abbreviations used for the books of Th. Cailleux (1878):
OC  Origine celtique de la civilisation de tous les peuples
PH  Poésies d' Homère
PA   Pays Atlantiques, decrit par Homère
Citations of Homer: Roman cyphers = Ilias, e.g. XX,345; Arabic cyphers = Odyssey, e.g. 13,34.

Bibliography Atlantic authors:
Homeros Odyssee, by Gerard Janssen, Leeuwarden 2018 = H.O.
Gideon E. Troje lag in Engeland, Deventer 1991, reprint of Homerus, zanger der Kelten, 1973
Grave Ch.J. De  République des Champs Élysées, Gent 1806, 3 vols.
Oosten H. van: Trojaanse tin-oorlog en Odysseus'oceaanroute 2020 (with English summary)
Vinci F. The Baltic Origins of Homer's Epic Tales, 2005
Wilkens I.J. Where Troy once stood, 1990,
                   Dutch: Waar eens Troje lag, 2015 Leeuwarden