Thomas James was the 18th century author of The History of the Herculean Straits, in which he offered support for the idea of Atlantis in America [1739.1.216].
Neville Chipulina, a Gibraltarian, concluded his blog on the Pillars(a) with a quote from James’ 1771 book, who said – “The reader will observe by the great disagreement of authors, the almost impossibility of absolutely vouching for the truth of any fact. ” In 1854, Wm. Smith’s Dictionary of Greek and Roman Geography  summed up this uncertainty regarding the Pillars of Herakles by noting that when the ancient writers began to investigate the matter more closely, they were greatly divided in opinion as to where the Pillars were to be sought, what they were, and why they were called by the name of Hercules.
The Strait of Gibraltar according to Greek mythology was created by Herakles. Neville Chipulina explains that “it seems that the person responsible for the myths about Hercules was Peisander of Rhodes, a 7th century BC Greek epic poet who apparently got the story from an unknown Pisinus of Lindus who almost certainly plagiarised it from somebody else. In other words it’s a pretty old story.”(c)
The Strait is very much a part of many current Atlantis theories. Primarily, it is contended that the region itself held the location of Atlantis. This is based on Plato’s statement that Eumelos, also known as Gadeirus, the twin brother of Atlas the first king of Atlantis gave his name to Gades, known today as Cadiz. Andalusia in Southern Spain has been the focus of attention for over a hundred years. In recent years Georgeos Diaz-Montexano and his rival Jacques Colina- Girard have been investigating the waters of the Strait itself while south of the Strait Jonas Bergman has advanced his theory that Atlantis was located just across the Strait in Morocco.
Although there is general acceptance that the Pillars of Heracles had their final resting place in the vicinity of the Strait of Gibraltar, it must be noted that there have been others candidates at different times with equally valid claims. The location of the ‘Pillars’ referred to by Plato at the time of Atlantis is the subject of continuing debate.
Strato, the philosopher, quoted by Strabo, spoke of a dam separating the Atlantic and the Mediterranean being breached by a cataclysm. This idea was reinforced by comment of Seneca. Furthermore, a number of Arabic writers, including Al-Mas’udi, Al-Biruni and Al-Idrisi, have all concurred with this idea of a Gibraltar land bridge in late prehistory.
A more radical theory is that of Paulino Zamarro who contends that the Strait was in fact closed by a landbridge during the last Ice Age because of the lower sea levels together with silting. When the waters rose and breached the landbridge, he believes that, the flood submerged Atlantis, which he situates in the Aegean. Others support Zamarro’s idea of a Gibraltar Dam amongst whom are Constantin Benetatos and Joseph S. Ellul.
Terry Westerman on his heavily illustrated website surveys impact craters globally. He suggests that “The Strait of Gibraltar was formed by two meteor impacts. The first blasted the round area in the western Mediterranean Sea to form a land bridge between Spain and Morocco.” He maintains that a second impact broke the landbridge around 5.33 million years ago, creating what is called the Zanclean Flood which refilled the then desiccated Mediterranean(d).
A German language website(a) presented some of the following data+, apparently recording the dramatic widening of the Strait of Gibraltar between 400 BC and 400 AD. The same list was included in the ‘Strait of Gibraltar’ entry of the German Wikipedia(b) until a few years ago. It has since been removed.
+Damastes of Sigeum, circa 400 BC. – about 1.3 km
+Pseudo-Skylax, probably fourth Century BC – about 1.3 km
*Turiano Greslio? 300BC – 8.0 km
*+Titus Livius (Livy) 59 BC- 17 AD – 10.5 km
+Strabo 63 BC- 24 AD – from 9.5 to 13.0 km
+Pomponius Mela , 50 AD – about the 15.0 km
+Pliny the Elder , 50 AD – about 15.0 km
*+Victor Vicensa (*Vitensa?), 400 AD – about 18 km
The above figures suggest that in the latter half of the first millennium BC, the Strait of Gibraltar was gradually widened. Nevertheless, until the methods used and all the data on offer have been verified, the idea must be treated with great caution.
My list had orignally included Euctemon, the 5th century BC Athenian astronomer, however, Werner E. Friedrich notes that Euctemon was referring to the Sea of Marmara near the entrance to the Black Sea [0695.38].
>However, more recently, John Jensen Jnr. has offered a comparable, if shorter, number of dates showing the reducing width of the strait the further back you go, from which he extrapolated that around 3450 YBP, when he believes that a landbridge there was breached(e).<
Georgeos Diaz-Montexano has also referred to the descriptions by ancient writers of the Strait of Gibraltar indicating a width of around two kilometres. Unfortunately, he does not cite references(f). He also is sympathetic to the existence an earlier landbridge at Gibraltar.