BOOKTEXT1

Contained within the First Book

1. Why Cartography differs from Chorography

2. What prior considerations are necessary for the study of Cartography

3. How, from measuring the stadia in a given distance, even if not on the same meridian, the stadia of the circumference of the Earth may be comprehended, and also the reverse.

4. It is necessary that one should believe out of proper observation and beware of traveller's tales.

5. Why one must attend, as closely as possible, to the results of current research because the Earth itself changes in relation to time.

6. Concerning the geographical observations of Marinus of Tyre.

7. Correcting the Earth's total latitude, as given by Marinus, from proper observations of distance.

8. Correction of observations by computing journeys by land.

9. Correction of observations by computing journeys by sea.

10. Ethiopia should not have been placed more southerly than the parallel opposite Meroe.

11. Concerning the fact that Marinus is not right when calculating the magnitude of the known world.

12. The determination of longitude being corrected from journeys by land.

13. Correcting similar calculations after completing voyages at sea

14. Concerning the voyage from the Golden Cheronese to Cattigara.

15. Concerning disagreement with some of the claims of Marinus.

16. In marking out certain provincial boundaries, he himself has transgressed.

17. Concerning matters he himself discourses upon relating to those having been enquired into today.

18. Concerning the inconvenient organization of Marinus when writing about the habitable Earth.

19. Concerning a means leading towards a convenient way in which we can graphically represent matters.

20. Concerning the asymmetrical nature of the cartographic maps of Marinus.

21. What it is necessary to observe for map making on a flat surface to be made possible.

22. How it is necessary to inscribe the habitable world on a sphere.

23. Explaining the categorisation of the inscriptions of meridians and parallels.

24. Cartographic method of representing the known world on a flat surface in correct proportion to that on a sphere.

THEORECTICAL CONSIDERATIONS

Section 1

Why Cartography differs from Chorograpy

§1. Cartography is the diagrammatic imitation of the known parts of the World with its unique features and it differs from Chorography since really this is the selecting out of certain regions as such to detail almost all the features in the smallest detail, and fixing in place such things as harbours, villages, towns and the course taken by rivers.

§2. The concern of Cartography is to determine the nature of the Earth by showing it as one whole, how it is formed and, from one given point, show a comprehensive circumscription with contours, the location of rivers, great cities and races of people most worthy of mention, and the shape of every one of the most distinguished features.

§3. In its ultimate role, Chorography holds the key to describing just one part of the above mentioned whole as if one represented just the ear or the eye alone. But Cartography is the viewing of the whole, the analogy being that concerned with showing the whole head.

§4. For the whole picture, as for a part of the whole picture, the scale must be adapted to what the eye can comfortably encompass. While Chorography renders the smallest particular in detail, Cartography represents whole countries according to their general features. Although in a representation of the world, prominent features should be commensurate in scale, distinctive features should still be included.

§5. Chorography is essentially qualitative in nature and concerned with the relative situation rather than exact position. Cartography is however quantitative since it involves the judgement of proportions as regards distances and regional boundaries and is relative only as regards outlines.

§6. Chorography needs skill in topography and no one, if not a draughtsman, should undertake it. On the other hand Cartography requires merely unadorned linear drawing with directional annotations, to direct the eye to a position, but otherwise the ability to create schematical arrangements.

§7. Because of the need for theses requirements the latter demands that a first rate mathematical ability to be pre–eminent. In short, while Cartography requires a mathematical ability, Chorography requires an artistic ability.

§8. For Cartography it is necessary to consider the outward appearance and magnitude of the Earth, to discover under which of the heavenly spheres its various parts lie and to appreciate the character of its known parts. From which can be ascertained the apportionment of days and nights and which fixed heavenly bodies lie above it and which below the horizon and all other things needed to interpret these phenomena.

§9. For it is the ultimate and most sublime contemplation of mankind to demonstrate by mathematical theorem an understanding of the heavenly firmament revolving about us and likewise of the Earth itself which, since it cannot be physically encompassed by one man, can at least be moulded into an image of itself.

Section Two:

What prior considerations are necessary for the study of Cartography

§1. What Cartography is about and its difference from Chorography has been discussed and laid down above.

§3. First it is necessary to establish the direction between any two points on the surface of the Earth and which alignment a direct line requires (whether, for example, to the North or to the East or to any point between). Such measurement is impossible without the use of the above instruments which, at any time or in any place, will determine the relationship of the points to that of the meridian line and the interval of the distance.

§4. Granted this and the subsequent translation into the number of stadia, it still will not provide the required answer since a journey is seldom in a straight line. Many deviations are required both on land and at sea. The calculation of the distance of a land journey will require a subtraction from the total stadia involved in the many deviations to achieve a direct distance while the calculation of the distance of a sea journey will require an allowance to be made for contrary winds and sea currents. Even if a distance is computed accurately however it will not tell us its relationship to the circumference of the Earth, the Equator or to the Earth's axis.

§5. However, through observation of the heavenly bodies, accurate determination of locations can be achieved and with them how the circumference can be divided by intersecting parallel circles, (or longitudes) and then similar circles, parallel to the meridian, (or latitudes), allowing each to be inscribed diagrammatically. The two locations for any journey will therefore be represented by the intersection of longitudinal and latitudinal readings. From these it will be easily seen how much distance is required from one location to another as it might be a part of a larger circle encompassing the Earth. This does not need the mere calculation of stadia based on travellers’ tales but requires an access to the map of the whole Earth.

§6. For it is sufficient to accept that the circumference of the Earth itself can be divided into parts, however small or large that one requires, and that such parts will inevitably be partly contained within distances inscribed on the great circle itself. It is not a good idea to actually divide the great circle into uneven parts to suit the number of stadia in any one particular journey.

§7. It is sufficient to calculate, by celestial observation, the number of stadia contained in a segment of the greatest circle whose ratio to the whole is known and, by extrapolation, arrive at the total number of stadia in the whole circumference of the Earth.

§8. Thus it may be proved by mathematics that the entire land and water surface of the Earth comprises a spherical object that exists around the central point of the heavenly sphere itself. The result being that any point on the surface of the Earth in common with this centre will make a great circle of its own. During the course of a day and a night this will cut the circumference of the Earth at proportionate intervals. While it follows that a distance measured in stadia on Earth can be correct, its proportion to the whole circumstance cannot be made known. By using celestial calculation this proportion can be calculated.

Section 3:

How, from measuring the stadia in a given distance, even if not on the same meridian, the stadia of the circumference of the Earth may be comprehended, and also the reverse

§1. Previously to this time, all who sought to make exact calculations of distances on Earth did so not only in order to comprehend the length of the greatest circle but also to be able to measure the segment occupied by such an equal proportion on one and the same meridian. Observing by the use of the instruments I have mentioned the marks of the highest point over each of the two opposite points of a distance, they calculated from the readings obtained an appropriate measurement of distance on the Earth.

§2. They assumed that at both of two points of any interval of distance, calculated by celestial observation, a longitudinal line intercepted a latitudinal line and that the distance between these two points along the same latitudinal line represented a fixed proportion of the circumference of the earth.

§3. It does not matter whether the measurement is along exact lines of longitude or latitude, any distance in any direction can be measured by the use of the instruments already mentioned, the astrolabe will fix the angle of elevation to the pole star and thus the longitude; the gnomon will fix the angle to the sun and thus the latitude. The calculation of distance can then be made.

§4. It follows that the circumference of the Earth can thus be calculated by such observations being used to measure a proportion of the equatorial circle passing under a vertical point over a known period of time. From there the full circumference can be extrapolated.

§5. So that any distance at any inclination on the surface of the Earth can be measured, if not directly, by ascertaining, using celestial observation, the ratio to that of the celestial reading for the total circumference of the Earth.

section 4:

It is necessary that one should believe out of proper observation and beware of travellers tales.

§1. Well then, these travellers, could they have availed themselves of such observations in this way, would have left behind them accurate description of the known parts of the Earth.

§2. But since Hipparchus alone has revealed the elevation of the pole star and, even then, classifying it from only so many of the places well known to geographers, and since these are on the same meridian those coming after him wishing to calculate distance to the North or South were unable to do so as they were not lying on the same meridian. They calculated such distances using traditional methods, not because they had no skill or were lazy but because the use of mathematics had not been developed. This was aggravated because not many lunar eclipses had been viewed simultaneously from two or more positions, as was the eclipse which when observed from Arbela occurred at the fifth hour, while at Carthage it was only at the second hour. It was thus established how much time separated two locations east to west and it only right and proper that a serious geographer should make use of such scientifically observed results and only make information from travellers tales secondary to this. By this means places on earth can be placed more accurately than by relying on the handing down of legend.

Section 5:

Why one must attend, as closely as possible, to the results of current research because the Earth itself changes in relation to time.

§1. Therefore, having made an attempt to write down the preliminaries in a straightforward manner, it would be best to make a beginning of the work and set forth.

§2. Regions in their entirety cannot be completely comprehended, because of their immensity or because they have not always uniformity. But passing time produces an altogether more accurate picture and Cartography takes account of such a kind of change. (For without contradiction legends change in relation to time itself, for many parts of the inhabited Earth, on account of their magnitude, we have as yet not obtained for ourselves more knowledge, others because information has not been obtained except out of unscientific reports of travellers, other parts have suffered change by reason of conflict or circumstance and become ruins.) It is necessary for us to watch out for and to devote ourselves to the latest information and from these reports extract what is credible and reject what is not.