It is characteristic of our history that a gap, almost entirely unbridged, exists between the early period and the sixteenth century in the story of the development of methods of precision in determining geographical position. We have already referred to early efforts to estimate the size of the earth, and in this connection have mentioned that simple instrument of unknown origin, the gnomon. Aristarchus improved upon the mere upright rod whose shadow was measured, by setting one upright in a bowl, the length of the rod and the radius of the bowl being equal; by means of this instrument, which was called the scaph, the angle of altitude could be read on a scale of circles inscribed on the inside of the bowl. Among other early instruments were the astrolabe, an invention attributed to Hipparchus, which served mariners and others down to the seventeenth century; the diopter, which appears to have resembled an alidade mounted on a stand, and may be regarded as a prototype of the theodolite; and Ptolemy’s rods, or the triquetum, in which a rod working upon two others, one vertical while the other pointed to the observed object, enabled the angular zenith distance to be read. It is true that some additions to this list of instruments were made by, or for the benefit of, medi?val mariners before the pregnant period about92 the beginning of the sixteenth century. Thus the less cumbrous quadrant was early brought into use, to the partial displacement of the circle of the astrolabe. The cross-staff, for measuring the angle between the horizon and the sun, is first described, so far as is known, in 1342.
Fig. 9.—Scaph.
(Front.)
(Back.)
Fig. 10.—Astrolabe.
Fig. 11.—Quadrant.
But it was not until the sixteenth century that the study of the earth’s size and figure began again to attract attention. The fact that it did so, and the interest that was thereafter maintained in this investigation, stand in the first instance to the honour of French science. The Spanish and Portuguese congress which attempted in 1524 to lay down the boundary fixed under93 the Pope’s award as separating the areas of Spanish and Portuguese dominion in the new world—a line lying 370 leagues west of the Cape Verd Islands—failed utterly; the length neither of a degree nor of a league could be agreed upon. Jean Fernel (1497–1558) in France, however, made measurements by calculation from the revolutions of a carriage wheel and by means of quadrant observations, and reached a fair estimate of a degree. A Dutchman, Willibrord Snell, who published his results in 1617, laid the foundation of modern methods of survey by applying to the measurement of an arc between Alkmaar and Bergen-op-Zoom the system of a series of triangles and the trigonometrical computation of the distance. During the century which intervened between the labours of Fernel and of Snell, it is clear that interest was waking in the development of precise methods of land-surveying, for the compass was probably first applied to this work at the beginning of the period; in 1571 we find Leonard Digges introducing in England an instrument which represented the theodolite at an early stage; and Jean Pretorius at Wittenberg in 1590, and Philip Danfrie in France in 1597, with his graphometer, foreshadowed that most valued equipment for detailed survey work, the plane-table.
Fig. 12.—Cross-staff.
An arc was measured and the length of the degree calculated in England by Richard Norwood in 1633–37. Important improvements in instruments appear about this time. Thus Fran?ois Vernier introduced in 1630 the microscopic attachment named after him the vernier, through which close and accurate reading of scales may be made. In 1643 appeared Torricelli’s barometer, and in 1648 Pascal, in France, applied the principle of the difference of atmospheric pressure at different elevations94 to the measurement of height above sea-level. A little later follows the application of the telescope to surveying instruments. In 1669 Jean Picard, measuring an arc in France, used a quadrant fitted with a telescope in which crossed wires were inserted, providing lines and a point (the intersection of the wires) in the field of observation, for the purpose of ensuring accuracy. Meanwhile, in 1657, Christian Huygens, a Dutch scientist, introduced (if he did not actually invent) the pendulum clock; and Jean Richer, using one in the course of astronomical work undertaken in South America for the French Academy of Sciences, found that the pendulum regulated to beat seconds in Paris failed to do so in Cayenne. This opened up the problem of the deviation of the earth’s figure from the true sphere; Sir Isaac Newton had argued such deviation to exist from mathematical theory associated with95 the rotation of the earth, and Huygens himself also investigated the question. Their conclusions, and that to be drawn from Richer’s pendulum observation, represented the earth as an oblate spheroid, or (in simpler expression) as somewhat flattened at the poles, the polar diameter being shorter than the equatorial. On this showing, a degree measured, let us say, in the north should be longer than one measured nearer the equator; but J. and D. Cassini, in the course of an extensive triangulation in France in 1684–1718, obtained an opposite result. Their measurements were subsequently proved inaccurate, but not before much controversy had arisen as to whether the earth is a prolate spheroid (as their results would go to prove), or oblate, as held by Newton and Huygens; and the French Academy had despatched expeditions to Peru and to96 Lappland, there to measure arcs for comparison. The Peruvian arc was measured by Pierre Bouguer and Charles de la Condamine in 1735–45, in the face of difficulties sufficiently reflected by the length of time occupied and by the fact that they fell out over the work and published separate accounts of it; the Lappland arc was worked out by P. L. M. de Maupertuis and his party in 1736–37.
Fig. 13.—Davis’s Back-staff.
Fig. 14.—Pretonius’s Plane-table.
It may be noticed that the difficulties of Bouguer and De la Condamine included troubles with untrustworthy instruments; but during the following half-century, while geodetic work proceeded apace in France, and was also carried on by measurements in South Africa, North America, and Italy, instruments making for greater precision were being designed.
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Fig. 15.—Ramsden’s Theodolite.
The instruments and data available during the sixteenth and seventeenth centuries had been fairly effective in skilled hands for the observation of latitude, but observations for longitude remained very difficult. Regiomontanus had prepared ephemerides for 1474–1506, and Columbus used them; Peter Apianus made a series for 1521–70, but the results continued to be far from accurate till the appearance of Kepler’s Rudolphine Tables in 1526. Harrison’s work on the chronometer had been anticipated as early as 1530 by Gemma Frisius, who indicated the possibility of using a clock in determining longitude; but even Huygens’s clock was not found effective for this purpose. In 1735, however, John Harrison’s first chronometer appeared, and afforded the accurate measurement of time under varying conditions which is essential to the calculation of longitude. About 1737 Jonathan Sission produced a theodolite, and later in the century Ramsden’s greatly improved theodolite (actually a pioneer instrument, greatly though its type was afterwards modified in detail) was constructed and brought into use in the98 trigonometrical survey of England and Wales, which was begun in 1784.
Fig. 16.—Modern five-inch transit Theodolite.
Meanwhile in this period cartography underwent an evolution from ancient to modern methods. It is impossible here to attempt any catalogue of even the principal cartographers, and the work of a few must be taken as typical. In the earlier part of the period (sixteenth century) the marine chart was still the most generally valuable of the cartographer’s wares; but he was already extending his stock in other directions. Thus Gerhard Kremer (1512–94), more famous under the name of Mercator, is principally known for his99 chart of the world on the familiar rectangular projection which bears his name; but his other activities, besides the production of an atlas, included that of maps of various special areas; and he carried out survey work himself in Flanders as the basis of a map of that territory, which he produced in 1540. Not only the projection named after him, but also the secant conical, are usually attributed to Mercator. Edward Wright, a mathematician of Cambridge, produced the first English map on Mercator’s projection, which indeed has been stated to be actually Wright’s own invention; on this map we should observe the omission of various imaginary and erroneous details common to maps of the period—notably the southern continent. But the renewal of the study of map-projection was mainly owing to German mathematicians, such as Werner of Nuremberg, and Apianus, in the first two decades of the century. In Mercator’s work there are to be observed various tendencies towards modern practice, such as the abolition of the old small sketches or miniatures representing towns and divers other subjects, and the introduction of symbols. On the other hand, the period of the application of criticism by the cartographer to the data before him was not yet come. Mercator was content to supplement data, where imperfect, by imagination; and that tendency is to be observed in other work of the period, as, for example, in the astonishing conception of the hydrography of Africa set forth by F. Pigafetta in 1591. However, the application of criticism and prompt attention to new sources of information soon became recognized as cartographers’ duties. Thus, Nicolas Sanson of Abbeville, who founded a famous map-making establishment in 1627, made a common practice of citing his authorities; and101 again, promptly upon the work of Jean Picard (noticed above) and others, in the determination of positions from 1669 to the end of the century, there followed the production of a map of France corrected according to these observations, which were also used in other French publications. On some of these appears—first about 1674—the earliest rude representation of relief by hachures, though the old practice of the cartographer, of drawing relief in a species of perspective, and thereby making a molehill on his map out of a mountain in nature, was by no means yet superseded. It was more than half-a-century later that the cartographers hit upon the contour-line. M. S. Cruquius adopted this method of showing relief on a chart of the Merwede in 1728; P. Buache similarly showed the depths of the English Channel in 1737; J. G. Lehmann used contours as the proper scientific basis of hachuring in 1783, and a contoured map of France was produced in 1791 by Dupain-Triel. The atlas of Germany, begun by a famous cartographer of Nuremberg, Homann, and published in 1753, illustrates successive stages in the evolution of hill-shading; for the earliest map in the series, dating from thirty-five years earlier, shows the first endeavour to differentiate the shading according to the steepness of slope. In the meantime the use of maps had already been recognized in some of the many special departments of geographical science from which they are now inseparable. For example, the variation of the compass had been mapped by C. Burrus early in the seventeenth century, and was more effectively worked out by the famous astronomer E. Halley in 1683. A. Kircher, again, took an early step in the department of oceanography by mapping currents and other features of the oceans in 1665.
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Fig. 17.—The World according to Mercator (1587).
From what has been written above, it may be inferred, and justly so, that Holland and France led the way in the development of cartography from the sixteenth to the eighteenth century. But by the end of the sixteenth century and throughout the seventeenth the mapping of most of the western European countries was rapidly extended, as in Germany, Austria, Switzerland, and Italy, in Denmark and Scandinavia, and in the British Isles. German local mapping ranked high, as appears from the collection in Ortelius’s Theatrum Orbis (1570) and from Mercator’s map of Germany (1585), both of which show the superiority of the cartographical material available for Germany. A large number of maps were based on original survey work. As early as 1566 a map of Bavaria by Philip Bienewitz, on a scale approximating (in terms of our survey) to two and a quarter miles to an inch, gave the results of a regular survey of remarkable accuracy for the period. Such was also the case (to select an example at home) with Christopher Saxton’s atlas of England and Wales (1574–79), in which the maps are about an inch to three miles in scale. This work marked the beginning of an important period in the history of British maps; Timothy Pont’s maps of Scotland appeared about 1608, and John Speed’s, of the British Isles on about the same scale as Saxton’s, in 1610. Hollar adopted a smaller scale (about five miles to the inch) in his maps of England and Wales dated 1644. These were of service in the Civil War, and the importance of military requirements in furthering the extension of organized survey work—which will appear in its subsequent history—is early exemplified in a survey of Ireland made under an Act of 1653; though this, the first British cadastral survey, was not103 a preliminary but a result of military operations, for it was made in connection with the parcelling of Irish lands among those who took part in the suppression of Irish rebellion. Again, the Scottish rebellion of 1745 led directly to a survey under Captain (afterwards General) Roy in 1747. It may be added here that in later cadastral work Ireland again took precedence of Great Britain: the six-inch survey begun in the former country in 1825 was nearly finished when that of Great Britain was undertaken in 1840.
France continued to lead the way in cartography in the eighteenth century. The maps of G. Delisle (1675–1726) and of J. B. B. D’Anville (1697–1782) were not merely confined to local work; they also included the presentation of cartographical material for distant lands selected according to truer scientific criteria. Thus D’Anville’s map of Africa, though preserving a few old inaccuracies, did away with details which were purely imaginary, and boldly revealed the then practically complete ignorance of the interior by representing it almost wholly as a blank. We may contrast this with earlier maps of the continent. Thus Waldseemüller (1516) showed waterways running parallel with the west coast, from north to south, and showed no conception of the Congo. Gastaldi (1564) marked the Zaire (Congo); but this and an east-flowing river and a branch of the Nile all flowed from a great central lake, Zembere. Mercator established a definite parting of the Nile, the Zaire, and the east-flowing system, though his ideas were still far from the truth.
English cartographers of the eighteenth century were inspired by the over-sea expansion of the empire to much good work beyond the home shores. Thus J. F. W. Desbarres in 1774–79 made use of the104 nautical surveys of James Cook and others in his Atlantic and North-American work. Thomas Jefferys produced West Indian and American atlases at the same time, and Aaron Arrowsmith founded a famous cartographical establishment, the work of which was carried on for a century. Mention is also due here of the work of Major James Rennell, who became surveyor-general of Bengal in 1763, and covered that territory in his atlas of Bengal (1779) on a scale of five miles to one inch, the work depending mainly upon route surveys and being, of its kind, extraordinarily good. The trigonometrical survey of England and Wales, already referred to as begun in 1784, owed its origin to French inspiration; for Cassini de Thury, who in 1740 had re-measured and found incorrect the work of J. and D. Cassini in France, represented the desirability of establishing a geodetic connection between Paris and Greenwich, and General William Roy was appointed to supervize the English work.
The revival of interest in earth-measurement and survey led directly to the furthering of the study of theoretical geography. We have happened already upon the names of Peter Apianus and Gemma Frisius in the history of the mathematical branch of geography; these two—Apianus by publishing in 1524 his Cosmographicus Liber, and Frisius by editing and expanding that work under the title of Cosmographia—re-founded the science on a mathematical basis, though they remained bound to the Ptolemaic view of a sharp distinction between geography, the general description of the world, and chorography, the particular description of a region. There is, perhaps, something characteristic in the insistence on this curiously arbitrary105 distinction; there has been sometimes a tendency to narrow the view of the field of “pure” geography on the part of workers labouring in one corner of it and turning their backs upon the rest. Indeed, at this very period is found another Cosmographia, to which its author added the epithet “universalis,” wherein the now familiar view of geography as a human and political field of study appeared, to the no less familiar exclusion of the mathematical aspect; for Sebastian Münster, in his work published in 1544, neglected the mathematical side entirely, modelling his work on that of Strabo. Philip Cluverius, again, in his Introduction to Universal Geography (1624), preserves the distinction between geography and chorography, albeit but one out of his six books deals with the earth at large, while in the rest countries are treated in detail, the human aspect being closely studied. Nathanael Carpenter of Oxford, however, threw over the distinction in so far as he recognized that neither geography, as distinguished by earlier writers from chorography, nor chorography itself, nor topography (under which term were classified the closer descriptions of smaller areas than those which belonged to chorography), was anything more than a part of a whole. Therefore, he divided his Geography (1625) into “spherical” and “topical” parts, the first dealing with the mathematical side, the second with different divisions of the earth according to physical, not political, considerations; his work is thus notable as indicating his realization of the function of geographical study which follows from those of measurement and description—namely, that of the correlation of phenomena. In 1650 appeared the Geographia Generalis of Bernhard Varenius, who died, still a young man, in that year. He laid down a broad division of106 the subject into general and special parts. His general part was sub-divided so as to include, firstly, the shape, size, and general physical characteristics of the earth, the distribution of land and water, land forms and hydrography; secondly, the astronomical and mathematical aspects, such as zones, latitude and longitude, the investigation of which was carried further in the third sub-division, which was comparative, dealing in this manner with data previously adduced. Varenius did not himself take up the special part of geography, though he defined it as also falling into three sub-divisions, the first of which should deal with the position, boundaries, physical features, and natural products of a country, the second with celestial and atmospheric conditions, and the third with the human element. This last was (as it still is) a popular branch of the subject which, for his own part, he would not have admitted; he held pure geography to be a matter apart from political and social considerations. But here was a geographical framework which, as H. R. Mill has pointed out, “was capable of accommodating itself to new facts, and was indeed far in advance of the knowledge of the period.” Being so, its worth was by no means generally recognized at first, although in 1672 Sir Isaac Newton put forth an annotated English edition for use in connection with lectures of his own. “The method included a recognition of the causes and effects of phenomena, as well as the mere fact of their occurrence, and for the first time the importance of the vertical relief of the land was fairly recognized.” The work found its place in time; the French and Dutch geographers, as well as the English, had it in their own tongues, and it became a standard, not only for the century of its original production, but for the next also.