The region described by Ptolemy as Celto–Galatia comprises the four Roman provinces of Aquitania. Lugdodensis, Belgica and Narbonensis and, in modern terms, cover the area from the Pyrennes and the Bay of Biscay to the Rhine and from the English Channel to the Mediterranean. As such it would have covered the modern countries of France, Holland, Belgium, Luxembourg and part of Switzerland and Germany. This section is concerned with the easternmost province of Aquitania.
Ptolemy gives the following outline to the province of Aquitania. The western boundary is taken up entirely with the waters of the Bay of Biscay, from the promontory at the northern end of the Pyrennes to the mouth of the Loire River. The northern boundary follows the Loire river to its source while the eastern boundary goes from this point towards the Pyrennes, making a north–western detour around the town of Tolosa (Toulouse), finally joining the mountain chain at a point coinciding with modern day Andorra. The southern boundary proceeds from this point to the promontory on the Bay of Biscay. For a comparison with modern co–ordinates, these points, in sequence, would be roughly Hendaye, Nantes, east of the town of Pradelles in the Massif Centrale and Andorra itself. On this basis, with the longitude reversed for purposes of comparison, the co–ordinates would be:
|Loire River Mouth||17°40'||48°30'||16°30'||47°12'|
|Loire River Source||21°00'||45°00'||21°45'||44°50'|
The modern day points of comparison for the Pyrennean Promontory and the mouth of the river Loire can only be approximated to Ptolemy. The exact point on the coastline of the Bay of Biscay for the former, and, in respect of the latter, what would be considered to be the actual river mouth two thousand years ago, are matters impossible of resolution. Yet even so, Ptolemy's framework of Aquitania is not greatly at odds with today's data and comes with a degree of compatibility sufficiently so to give us confidence in the remainder.
Ptolemy provides a list of nineteen towns in Aquitania, thirteen of which can be positively identified with locations mentioned in the Atlas of the Roman World, Cornell and Matthews, map 128/9, gazetteer 231/236:, one of tentative provenance and five for whom only speculation will serve. Of course, Cornell and Matthews list considerably more locations than Ptolemy, giving them modern day co–ordinates; some of them of quite significant size but, once again, we cannot know what occasions their absence from Ptolemy’s text, or what part the commentaries of Marinus played in their non–selection. The towns are:
|Ratiatum (opposite Nantes)||17°45'||48°20'||Unknown||Unknown|
|Augustan Springs (Aquae Tarbellicae)||17°00'||44°40'||16°57'||43°43'|
|Lugdunum Colonia (Lugdunum Converarum)||17°00'||44°00'||18°34'||43°02'|
In nine of the comparisons there is a standard error factor that once again maintains a consistent average and these are assumed to be the work of Marinus. The remainder, including three which include 'Augustus' in their titles and were presumably established in his time, show a familiar slippage in longitude to the east (see the 'turning of Scotland' above) and sustain a reasonable argument that they may well have been incorrect insertions by Ptolemy himself.
So, in Aquitania, we have the opportunity to compare an established Roman province, that contains no problems such as that of Britannia, directly with Ptolemy. From this comparison it is only fair to state that Ptolemy's text emerges reasonably unscathed, or rather, that part of it that one might reasonably ascribe to the commentaries of Marinus. It gives us confidence to continue with the other provinces and regions, that follow, with the knowledge that the co–ordinates given by Ptolemy have either a firm basis in fact or display a known error condition where they are the result of an insecure annotation.
Ptolemy defines the outline of Lugdudensis in §1/4. The western side continues from the Aquitanian border, at Nantes along the upper Bay of Biscay to Brest. From there the northern side is defined along the English Channel coast to the mouth of the river Seine. From there the eastern border follows the river Seine to its source then continues in a straight line to a point in the Jura mountains east of Geneva, somewhere around Oyonax where it joined the common border with the province of Narbonensis. From there the border proceeded south-westwards along the Narbonensis border until the point, east of Pradelles where the Aquitainian border abuts; the remaining side follows the northern bank of the river Loire down to Nantes. Ptolemy is not particularly specific about the actual section from the source of the Seine to the junction with Narbonensis but in order to include Lugdunum, from which the province takes its name, the boundary must take such a course. Cornell and Matthews, map 128/9 show the borders meeting as far north as the latitude of Geneva, on the mountains to the west of Lac Leman. A comparison of co–ordinates give the following data:
|Seine river mouth||20°00'||51°30'||18°55'||49°50'|
|Seine river source (contd.)||25°00'||45°30'||23°50'||46°04'|
|Loire river source||20°00'||45°00'||21°45'||44°50'|
Apart from Nantes, all the modern day reference points are problematical but even so, as with Aquitania, there is a reasonable pattern for comparison allowing for the standard error factor. Ptolemy's outline for Lugdudensis can be accepted as a basis for considering further locations within its interior.
There are twenty–eight locations listed by Ptolemy for the province of Lugdudensis and eighteen of these have clear Roman equivalents in the generally accepted source material. A comparison of co–ordinates give the following:
|Brinates (Portus Nameton)||17°40'||48°45'||16°27'||47°12'|
|Noeomagus Caleti (Noviomagus)||19°30'||51°10'||18°14'||49°09'|
|Segusianorum Market (Forum Segusiavorum)||20°30'||45°30'||22°13'||45°44'|
Of the eighteen locations of Ptolemy that have Roman equivalents, thirteen have an average error factor of +11% in keeping with the standard longitudinal deviation already mentioned. These might reasonably be attributed to Marinus. Of the remaining five, four including Lugdunum itself, mostly display parity, while the remaining one, Forum Segusiavorum, is placed much too far to the west. Ptolemy himself might reasonably interpret these as insertions. Augustobona and Augustodunum are presumably Augustan sites, as indeed is Lugdunum itself; Cavillonum and Forum Segusiavorum may be reasonably interpreted as some form of inter–urban spread generated from such a major centre.
There is little in this province that proves controversial to what has gone before. The standard deviation of longitudes attributable to Marinus continues to hold good, Ptolemy's co–ordinates in a relatively static, non–expansionist environment are reasonably in line with actuality. What does seem to be emerging is that Marinus can now be dated to a fairly precise time band between Julius and Augustus; that is to the peak of their respective power bases, when cities were being dedicated to them. Marinus seems to include Julian creations but excludes Augustan creations. On this basis his commentaries might reasonably be assumed to date from 50/45BC. a conclusion that could explain many of the puzzling features on some maps, such as that of Britannia.
In §1/6 Ptolemy outlines the province of Belgica, including upper and lower Germania. The western boundary is a mirror image of the eastern boundary of the province of Lugdudensis, already described. The northern boundary is along the coast of the Britannic Sea up to the mouth of the river Rhine and the eastern boundary follows the Rhine to its source and then deviates south westwards to a point in the Jura mountains where the borders of Lugdudensis and Narbonensis also join. The cardinal extremities are as follows:
|Sequana river mouth||20°00'||51°30'||18°55'||49°50'|
|Eastern throat of the Rhine||28°00'||54°00'||23°55'||51°58'|
|Rhine river source||29°20'||46°00'||27°45'||47°30'|
|Sequana river source||25°00'||45°30'||23°50'||46°04'|
All of these boundaries follow natural limits and it is only in the identification of the river sources that Ptolemy presents us with points of identification. Also the mouth of the Rhine two thousand years ago can only be assumed and the Nijmegen/Arnhem area would seem to be indicated by Ptolemy's co–ordinates. However there seems no great problem in comparison, given the standard error factor that prevails.
There are thirty–seven locations noted for Belgica with Upper and Lower Germania. Of these, twenty–three have definite Roman source references. the locations are:
One of the most conspicuous features of the list are the north/south string of fortified habitations along the western bank of the Rhine, mostly on the same longitudinal reading and occurring about every half degree of latitude. The majority of these show the standard error factor of +11% in longitude and these would appear to be earlier sites and the work of Marinus. Others, probably insertions by Ptolemy himself, would appear to be Augustan or later. It is not possible to comment further as to what extent these latter reflect the Roman expulsion from greater Germany. The remainder of the locations, for which Roman equivalents are to be found, are mostly assumed to be from data by Marinus.
As was to be expected, with such sensitive regions as Upper and Lower Germania, this province contains a greater number of locations for which there is a Roman provenance. The date we have provisionally assigned to the commentaries of Marinus, upon which Ptolemy based much of his work, would have seen the locations on the western bank of the Rhine as supply and communication centres rather than defensive bulwarks in themselves. After the Varian disaster, they became a de facto frontier and it is interesting to see the changes that had to be made actually occurring within the locations that Ptolemy gives. Beyond this there are no surprises within the province of Belgica. Lying as it did on the itinerary routing between Massilia and Gesoriacum, it was expected to contain a higher proportion of older sites. The other three provinces of Gaul were more inclined to be the main areas of Roman expansion.
The southern border of this province is formed by the eastern Pyrennes and the Mediterranean coast as far as Nice. The northern border is formed by the borders to Aquitania and Lugdudensis respectively and the eastern border, from Geneva to the Mediterranean is formed by the three Alpine provinces – Graiae & Poennae, Cottiae and Maritimae respectively. There is no effective western border except that part of Aquitanian border that swings around Tolouse. The cardinal points are,
|Aquitanian Border (Andorra)||19°00'||43°10'||19°45'||42°40'|
|Shrine of Aphrodite||20°20'||42°20'||21°10'||42°26'|
|River Varus mouth at Nice||27°00'||43°00'||25°09'||43°40'|
|Lake Leman (Geneva)||27°15'||45°00'||24 29'||46 22'|
Ptolemy lists thirty–two inhabited settlements in Narbonensis of which twenty–one are immediately recognisable as later Roman settlements,
|Sextia Colonia (Aquae Sextae)||24°30'||43°40'||23°27'||43°31'|
As regards tribal groups, the Volcae are mentioned together with the Allobrogi, Voconti and various other smaller groups including some that appear to have been based on single town states in the Greek manner.