Research Notes


Map Group PTOLEMY 1793
Ptolemy 1793
Map, Albion et Hibernia Britannicae Insulae, the British Isles from Ptolemy's data, engraved by Basire, published by the Society of Antiquaries, London, 1793.
This Ptolemy Map of Britain, 1793, from the data of Claudius Ptolemy, is plate 3 in Military Antiquities of the Romans in Britain by Willliam Roy, published by the Society of Antiquaries of London, 1793. The map studied is in a private collection.
The map size is: wxh, sheet = 64.5x55cm; wxh, plate = 577x467mm; wxh, map = 558x435mm.
The geographical data, a world gazetteer 'Geographia', was compiled by Claudius Ptolemy and later used by various cartographers to draw maps, often referred to as Ptolemy maps, about the 15-16th centuries. This late 18th century map is 'after' the plot by Gerhard Mercator.
NOTE BENE: these notes are not a general appraisal of this or any other Ptolemy map. While some general comments are made, the emphasis is strongly biased to Hampshire interest. The Geography is available in translation, and many people have commented upon its interpretation, see under REFERENCES.
 
MAP FEATURES
1793 MAP COORDINATES
PTOLEMY'S GEOGRAPHY
REFERENCES
ITEMS in the Collection
The title page of Roy's Roman Britain:-
THE MILITARY ANTIQUITIES OF THE ROMANS IN BRITAIN. BY THE LATE WILLIAM ROY, F.R.S. F.S.A. MAJOR-GENERAL OF HIS MAJESTY'S FORCES, DEPUTY QUARTER-MASTER GENERAL, AMD COLONEL OF THE THIRTIETH REGIMENT OF FOOT. PUBLISHED BY THE ORDER, AND AT THE EXPENCE OF, THE SOCIETY OF ANTIQUARIES OF LONDON.
LONDON: PRINTED BY W. BULMER AND CO., AND SOLD AT THE APARTMENTS OF THE SOCIETY, IN SOMERSET-PLACE; AND BY MESSRS. WHITE, BROWN, AND EGERTON. MDCCXCIII.
The map is plate 3 of a series of 50 plates at the back of the book. There is no obvious section of text that specifically describes the plate.
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MAP FEATURES
title    
map maker    
engraver    
Printed across the top:-
ALBION et HIBERNIA BRITANNICAE INSULAE Secundum CLAUDIUM PTOLOMAEUM Ex Exemplo Mercatoris amplificato
? which might be rendered:-
Albion and Hibernia islands of Britain, by Claudius Ptolemy after the example of Mercator
Printed at the bottom:-
Basire sc. / Sumptibus Soc. Antiquar, Londini Publish'd according to act of Parliament, April 23d. 1793.
orientation    
up is N    
The map has no indicator of orientation except the scales of latitude and longitude. The map is printed with North at the top of the sheet.

scale    
The map has no scale line. Bearing in mind the 'strange' shape of the plot, it is still possible to make a crude estimate of scale from the positions of places. The best way to do this would be to use many places, and the DISTTAB.exe software used for map of Hampshire. Failing this I have estimated the scale from the positions of only two measurements:-
Londinium - Eboracum = 110.0mm
London to York is 348.7Km gives a scale 1 to 3200000, 50 miles to 1 inch. And:-
Londinium - Aquae Calidae = 45.5mm
London to Bath is 178.0Km gives a scale 1 to 3900000, 62 miles to 1 inch.
A second approach is to use the scale of latitude, on which 5 degrees = 163.5mm, giving a scale 1 to 3400000, 54 miles to 1 inch.
Very roughly the scale of the map is:-
1 to 3500000
55 miles to 1 inch
There is a suggestion that the south parts are stretched E-W.

lat and long scales    
image snip from map
There are scales of latitude and longitude for a trapezoid projection, printed in the borders of the map; marked at 10 minute intervals, labelled at degrees. These are necessary to plot Ptolemy's data, which is just lists of places with their coordinates. The map maker has chosen a meridian, 20d E, through the east side of London to be vertical. The prime meridian of Ptolemy's longitude figures is in the Canary Islands. The map includes from 4d to 35d E, 51d to 63d 30m N. The British Isles including the Orkneys, and parts of the coasts of France and Germany. NB these are Ptolemy's coordinates, don't mistake them for modern values!
For Hampshire the
longitude, Winchester = 18d 50m E
Each of Ptolemy's places from The Geography is plotted by a neat, clear circle using his coordinates, and labelled in Latin.

sea area    
sea plain    
The sea area is plain, tinted pale blue for a distance off shore. The main sea areas are named by Ptolemy, eg:-
BRITANNICUS OCEANUS
for the English Channel.

coast line    
coast form lines    
image snip from map
The coast line is emphasised by form lines, tinted a mid blue.

rivers    
image snip from map
Rivers are drawn by a wiggly line tapering inland from an estuary which has form lines continued from the coast. Only the rivers listed by Ptolemy are shown, but the inland course is made up by the map maker, Ptolemy gives only the location of the river mouth, marked on the map by a circle.
Of Hampshire interest are:-
Alaunis Fl.
Trisanton Fl.
country    
The two mainlands of the British Isles are labelled and tinted. Pale yellow for:-
ALBION BRITANNICA
ie England, Wales and Scotland. Pale pink for:-
HIBERNIA
A darker wash of the tint emphasises the landward side of each coast line. On the european mainland:-
GALLIAE PARS
GERMANIAE PARS
are similarly labelled and tinted. Various islands are shown, including:-
Vectis
the Isle of Wight. Ptolemy give the coordinates of the centre of the island, nothing more. The map maker has allocated a size and shape.

tribal areas    
image snip from map
British tribal areas are bounded by dotted line, tinted yellow. Ptolemy lists his places under tribes which are roughly position relative to one another. He gives no boundaries, which are made up by the map maker. The tribal areas are labelled, for example around Hampshire:-
BELGAE
DUROTRIGES
REGNI
in south central England.

settlements    
Settlements are positioned by a circle, plus a church with a tower, spire and cross. Larger places like London have a few more buildings. All are labelled equally in upright lowercase text.
The places relevant to Hampshire are:-
image snip from map
Venta
Magnus Portus
Caleva
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1793 MAP COORDINATES
The coordinates of places can be read off the 1793 map. This is not made easy by the lack of collinearity of the slanted marks for minutes and degrees in top and bottom scales of longitude! Readings can be made to an error about plus/minus 2 minutes, though they are quoted below to 1 minute. Values read are in degrees and minutes.
It seems clear from the values, and from the spellings of labels that the version of The Geography used for this map is not the same as that translated by Stevens. These notes are not the place to investigate this problem; nor have I the competence.

SOUTH ENGLAND
       
label   longitude E latitude N
       
Ocrinum Prom.   12 00 51 30
Cenio Fl.   13 57 51 43
Voliba   14 38 52 20
Tamare   14 54 52 13
Uxella   14 58 52 46
Tamarus Fl.   15 48 52 12
Isaca Fl.   16 53 52 20
Legio II Augusta   16 59 52 31
Isca   17 31 52 45
Dunium   17 57 52 39
Alaunis Fl.   18 18 52 21
Venta   18 47 53 29
Magnus portus   19 00 52 59
Vectis   19 15 52 20
Neomagus   19 37 53 32
Londinium   19 60 54 00
Trisanton Fl.   20 10 52 59
Novus portus   20 51 53 30
Darvernum   21 00 53 38
Rutupia   21 42 54 01
Canium Prom.   21 54 53 59

PLACES
Rivet and Smith provide the following list of place interpretations; the places which seem to be relevant to Hampshire:-
Caleva    
in the region of the Atrebati
Calleva Atrebatum
Silchester; the town in the woods of the Atrebati.

Magnus Portus    
ie great harbour; probably a descriptive term, not a place name.
The area behind the Isle of Wight, ie the Solent and Southampton Water.

Venta    
in the region of the Belgae
Venta Belgarum
Winchester; the market town of the Belgae.

Alaunus Fl    
River Axe flowing into the sea at Seaton, Devon
OR
Rivers Stour and Avon flowing together into the sea at Christchurch, Dorset - both these two rivers have tributaries 'Allen'.

Trisantonis Fl    
River Arun flowing into the sea at Arundel, West Sussex.


PLOTTING THE DATA
Being unable to copy from Ptolemy's maps we can only use the coordinates of his listed features along coasts, and places inland, to plot a map. For the British Isles a rectangular grid was 'allowed' as suitable by Ptolemy, but the maker of this map has chosen a trapezoid projection to give a better representation. For the south of England, where lies Hampshire, it will make little difference. The relative proportions of latitude and longitude scales also has to be chosen, though considering the accuracy of the data the choice is unimportant for just the Hampshire area.
A purist approach to plotting the data provides a series of coastal points which can only, honestly, be joined up by straight lines! This style of map is drawn by Rivet and Smith (fig 1, p.107). The angularity might be softened without real loss of truth. But there is no evidence for more detail than this; the maker of the 1793 map has, like predecessors in the 15th century, added a lot of information ... from somewhere.
 
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PTOLEMY'S GEOGRAPHY
The Geography of Claudius Ptolemy dates from the 2nd century; he lived from about AD90-168. In it he gathered the best gazetteer of places with coordinates of longitude and latitude that he could, for the whole known world, over 8000 places.
The following extracts are relevant to Hampshire:-
Book 2
The Second Book contains the following:
A prologue of the particular descriptions, and a description of the western part of Europe ...
1. Hibernia island of Britannia ... Map 1
2. Albion island of Britannia
... ...
Prologue
... let us distinguish, in the descriptions, the various prefectures, and provinces of the earth. ... in accord with the known positions of localities ... ... In this way the opportunity will be given to any one, who desires it, for drawing the parts of the earth in maps according to the particular prefectures and provinces, one or many, and the right relation of the places of each other on the maps will be preserved, together with the right size and the right shape.
...
Having stated these things, let us begin our particular description with the western part of Europe according to its provinces or prefectures.
... ...
Chapter 2 has:-
Location of Albion island of Britannia (First map of Europe)
... ...
Damnonium or Ocrium promontory .. .. 12 __ 51 30
Description of the south side below which is the Britannicus ocean. After the Ocrium promontory is the mouth of the Cenio river .. .. 14 51 51 45
mouth of the Tamarus river .. .. 15 40 52 10
mouth of the Iscas river .. .. 17 40 52 20
mouth of the Alaunus river .. .. 17 40 52 40
Great harbour .. .. 19 __ 53 __
mouth of the Trisantonis river .. .. 20 20 53 __
New harbour .. .. 21 __ 53 30
Cantium promontory .. .. 22 __ 54 __
... ... Next to these are the Dobuni, and their town Corinium .. .. 18 __ 54 10
then the Atrebati and their town Caleva .. .. 19 __ 54 15
Next to these, but farther eastward, are the Canti among whom are the towns Londinium .. .. 20 __ 54 __
Daruernum .. .. 21 __ 54 __
Rutipie .. .. 21 45 54 __
Below the Atrebati, and the Canti are the Regni and the town
Neomagus .. .. 19 45 53 5
Below the Dobuni are the Belgae and the towns
Iscalis .. .. 16 __ 53 40
Aquae Calidae .. .. 17 20 53 40
Venta .. .. 18 40 53 __
Towards the west and south of these are the Durotriges whose town is
Dunium .. .. 18 __ 52 40
Next to these, but more to the west, are the Dumnoni whose towns are
Voliba .. .. 14 45 52 __
Uxella .. .. 15 __ 52 45
Isca, where is located Legio II Augusta .. .. 17 30 52 45
... ...
Below Magnus Portus is the island Vectis, the middle of which is in .. .. 19 20 52 20
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REFERENCES
Ptolemy, Claudius & Stevenson, Edward L (trans, ed): 1991: Claudius Ptolemy The Geography: Dover (New York, New York, United States):: ISBN 0 486 26896 9 (pbk)

Rivet, A L F & Smith, Colin: 1979: Place Names of Roman Britain: Batsford (London):: 0 7134 2077 4

Roy, William: 1793: Military Antiquities of the Romans in Britain: Society of Antiquaries of London (London)

ITEMS  in HMCMS Map Collection   (scanned item in bold)
  HMCMS:FA2002.651 -- map
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