A Mathematical and Philosphical Dictionary
, the science that teaches and explains the nature and properties of the earth, as to its figure, place, magnitude, motions, celestial appearances, &c, with the various lines, real or imaginary, on its surface.
Geography is distinguished from Cosmography, as a part from the whole; this latter considering the whole visible world, both heaven and earth. And from Topography and Chorography, it is distinguished, as the whole from a part.
Golnitz considers Geography as either exterior or interior: but Varenius more justly divides it into General and Special; or Universal and Particular.
General or Universal Geography, is that which considers the earth in general, without any regard to particular countries, or the affections common to the whole globe: as its sigure, magnitude, motion, land, sea, &c.
Special or Particular Geography, is that which contemplates the constitution of the several particular regions, or countries; their bounds, figure, climate, seasons, weather, inhabitants, arts, customs, language, &c.
History of Geography. The study and practice of Geography must have commenced at very early ages of the world. By the accounts we have remaining, it seems this science was in use among the Babylonians and Egyptians, from whom it passed to the Greeks first of any Europeans, and from these successively to the Romans, the Arabians, and the western nations of Europe. Herodotus says the Greeks first learned the pole, the gnomon, and the 12 divisions of the day, from the Babylonians. But Pliny and Diogenes Laertius assert, that Thales of Miletus, in the 6th century before Christ, first found out the passage of the sun from tropic to tropic, and it is said was the author of two books, the one on the tropic, and the other on the equinox; both probably determined by means of the gnomon; whence he was led to the discovery of the four seasons of the year, which are determined by the equinoxes and solstices; all which however it is likely he learned of the Egyptians, as well as his division of the year into 365 days. This it is said was invented by the second Mercury, surnamed Trismegistus, who, according to Eusebius, lived about 50 years after the Exodus. Pliny expressly says that this discovery was made by observing when the shadow returned to its marks; a clear proof that it was done by the gnomon. It is farther said that Thales constructed a globe, and represented the land and sea upon a table of brass. Farther that Anaximander, a disciple of Thales, first drew the figure of the earth upon a globe; and that Hecate, Democritus, Eudoxus, and others, formed Geogra- phical maps, and brought them into common use in Greece.
Meton and Euctemon observed the summer solstice at Athens, on the 27th of June 432 years before Christ, by watching narrowly the shadow of the gnomon, with the design of fixing the beginning of their cycle of 19 years.
Timocharis and Aristillus, who began their observations about 295 B. C., it seems first attempted to fix the latitudes and longitudes of the fixed stars, by considering their distances from the equator, &c. One of their observations gave rise to the discovery of the precession of the equinoxes, which was first remarked by Hipparchus about 150 years after; who also made use of their method, for delineating the parallels of latitude and the meridians, on the surface of the earth; thus laying the foundation of this science as it now appears.
The latitudes and longitudes, thus introduced by Hipparchus, were not however much attended to till Ptolomy's time. Strabo, Vitruvius, and Pliny, have all of them entered into a minute geographical description of the situation of places, according to the length of the shadows of the gnomon, without noticing the longitudes and latitudes.
Maps at first were little more than rude outlines, and topographical sketches of different countries. The earliest on record were those of Sesostris, mentioned by Eustathius; who says, that “this Egyptian king, having traversed great part of the earth, recorded his march in maps, and gave copies of them not only to the Egyptians, but to the Scythians, to their great astonishment.” Some have imagined with much probability, that the Jews made a map of the Holy Land, when they gave the different portions to the nine tribes at Shiloh: for Joshua tells us that they were sent to walk through the land, and that they described it in seven parts in a book; and Josephus relates that when Joshua sent out people from the different tribes to measure the land, he gave them, as companions, persons well skilled in geometry, who could not be mistaken in the truth.
The first Grecian map on record, was that of Anaximander, mentioned by Strabo, lib. 1, p. 7, supposed to be the one referred to by Hipparchus under the designation of the ancient map. Herodotus minutely describes a map made by Aristagoras tyrant of Miletus, which will serve to give some idea of the maps of those times. He relates, that Aristagoras shewed it to Cleomenes king of Sparta, to induce him to attack the king of Persia at Susa, in order to restore the Ionians to their ancient liberty. It was traced upon brass or copper, and seems to have been a mere itinerary, containing the route through the intermediate countries which were to be traversed in that march, with the rivers Halys, the Euphrates, and Tigris, which Herodotus mentions as necessary to be crossed in that expedition. It contained one straight line called the Royal Road or Highway, which took in all the stations or places of encampment from Sardis to Susa; being 111 in the whole journey, and containing 13,500 stadia, or 1687 1/2 Roman miles of 5000 feet each.
These itinerary maps of the places of encampment were indispensably necessary in all armies and marches; and indeed war and navigation seem to be the two grand causes of the improvements both in Geography and astronomy. Athenæus quotes Bæton as author of a work intitled, The encampments of Alexander's march; and likewife Amyntas to the same purpose. Pliny observes that Diognetus and Bæton were the surveyors of Alexander's marches, and then quotes the exact number of miles according to their mensuration; which he afterwards confirms by the letters of Alexander himself. The same author also remarks that a copy of this great monarch's surveys was given by Xenocles his treasurer to Patrocles the geographer, who was admiral of the fleets of Selencus and Antiochus. His book on geography is often quoted both by Strabo and Pliny; and it seems that this author furnished Eratosthenes with the principal materials for constructing his map of the oriental part of the world.
Eratosthenes first attempted to reduce Geography to a regular system, and introduced a regular parallel of latitude, which began at the straits of Gibraltar, passed eastwards through the isle of Rhodes, and so on to the mountains of India, noting all the intermediate places through which it passed. In drawing this line, he was not regulated by the same latitude, but by observing where the longest day was 14 hours and a half, which Hipparchus afterwards determined was the latitude of 36 degrees.
This first parallel through Rhodes was ever after considered with a degree of preference, in constructing all the ancient maps; and the longitude of the then known world was often attempted to be measured in stadia and miles, according to the extent of that line, by many succeeding geographers.
Eratosthenes soon after attempted not only to draw other parallels of latitude, but also to trace a meridian at right angles to these, passing through Rhodes and Alexandria, down to Syene and Meroë; and at length he undertook the arduous task of determining the circumference of the globe, by an actual measurement of a segment of one of its great circles. To find the magnitude of the earth, is indeed a problem which has engaged the attention of astronomers and geographers ever since the spherical sigure of it was known. It seems Anaximander was the first among the Greeks who wrote upon this subject. Archytas of Tarentum, a Pythagorean, famous for his skill in mathematics and mechanics, also made some attempts in this way; and Dr. Long conjectures that these are the authors of the most ancient opinion that the circumference of the earth is 400,000 stadia: and Archimedes makes mention of the ancients who estimated the circumference of the earth at only 30,000 stadia.
As to the methods of measuring the circumference of the earth, it would seem, from what Aristotle says in his treatise De Cœlo, that they were much the same as those used by the moderns, deficient only in the accuracy of the instruments. That philosopher there says, that different stars pass through our zenith, according as our situation is more or less northerly; and that in the southern parts of the earth stars come above our horizon, which are no longer visible if we go northward. Hence it appears that there are two ways of measuring the circumference of the earth; one by observing sta<*> which pass through the zenith of one place, and do not pass through that of another; the other, by observing some stars which come above the horizon of one place, and are observed at the same time to be in the horizon of another. The former of these methods, which is the best, was followed by Eratofthenes at Alexandria in Egypt, 250 years before Christ. He knew that at the summer solstice, the sun was vertical to the inhabitants of Syene, a town on the confines of Ethiopia, under the tropic of cancer, where they had a well made to observe it, at the bottom of which the rays of the sun fell perpendicularly the day of the summer solstice: he observed by the shadow of a wi<*>e set perpendicularly in an hemispherical bason, how far the sun was on that day at noon distant from the zenith of Alexandria; when he found that distance was equal to the 50th part of a great circle in the heavens. Then supposing Syene and Alexandria under the same meridian, he inferred that the distance between them was the 50th part of a great circle upon the earth; and this distance being by measure 5000 stadia, he concluded that the whole circumference of the earth was 250,000 stadia. But as this number divided by 360 would give 694 4/<*> stadia to a degree, either Eratosthenes himself or some of his followers assigned the round number 700 stadia to a degree; which multiplied by 360, makes the circumference of the earth 252,000 stadia; whence both these measures are given by different authors, as that of Eratosthenes.
In the time of Pompey the Great, Posidonius determined the measure of the circumference of the earth by the 2d method above hinted by Aristotle, viz, the horizontal observations. Knowing that the star called Canopus was but just visible in the horizon of Rhodes, and at Alexandria finding its meridian height was the 48th part of a great circle in the heavens, or 7 1/2 deg., answering to the like quantity of a circle on the earth: Then, supposing these two places under the same meridian, and the distance between them 5000 stadia, the circumference of the earth will be 240,000 stadia; which is the first measure of Posidonius. But according to Strabo, Posidonius made the measure of the earth to be 180,000 stadia, at the rate of 500 stadia to a degree. The reason of this difference is thought to be, that Eratosthenes measured the distance between Rhodes and Alexandria, and found it only 3750 stadia: taking this for a 48th part of the earth's circumference, which is the measure of Posidonius, the whole circumference will be 180,000 stadia. This measure was received by Marinus of Tyre, and is usually ascribed to Ptolomy. But this measurement is subject to great uncertainty, both on account of the great refraction of the stars near the horizon, the difficulty of measuring the distance at sea between Rhodes and Alexandria, and by supposing those places under the same meridian, when they are really very different.
Several geographers afterwards made use of the different heights of the pole in distant places under the same meridian, to find the dimensions of the earth. About the year 800, the khalif Almamun had the distance measured between two places that were 2 degrees asunder, and under the same meridian in the plains of Sinjar near the Red Sea. And the result was, that the degree at one time was found equal to 56 miles, and at another 56 1/3 or 56 2/3 miles.
The next attempt to find out the circumference of the earth, was in 1525, by Fernelius, a learned philosopher of France. For this purpose, he took the height of the pole at Paris, going from thence directly northwards, till he came to the place where the height of the pole was one degree more than at that city. The length of the way was measured by the number of revolutions made by one of the wheels of his carriage; and after proper allowances for the declivities and turnings of the road, he concluded that 68 Italian miles were equal to a degree on the earth.
According to these methods many other measurements of the earth's circumference have since that time been made, with much greater accuracy: a particular account of which is given under the article Degree.
Though the maps of Eratosthenes were the best of his time, they were yet very imperfect and inaccurate. They contained little more than the states of Greece, and the dominions of the successors of Alexander, digested according to the surveys abovementioned. He had indeed seen, and has quoted, the voyages of Pythias into the great Atlantic ocean, which gave him some faint idea of the western parts of Europe; but so imperfect, that they could not be realized into the outlines of a chart. Strabo says he was very ignorant of Gaul, Spain, Germany, and Britain; and he was equally ignorant of Italy, the coasts of the Adriatic, Pontus, and all the countries towards the north.
Such was the state of Geography, and the nature of the maps, before the time of Hipparchus. He made a closer connection between Geography and astronomy, by determining the latitudes and longitudes from celestial observations.
War has usually been the occasion of making or improving the maps of countries; and accordingly Geography made great advances from the progress of the Roman arms. In all the provinces occupied by that people, camps were every where constructed at proper intervals, and good roads made for communication between them; and thus civilization and surveying were carried on according to system, through the whole extent of that large empire. Every new war produced a new survey and itinerary of the countries where the scenes of action passed; so that the materials of Geography were accumulated by every additional conquest. Polybius says, that at the beginning of the second Punic war, when Hannibal was preparing his expedition against Rome, the countries through which he was to pass were carefully measured by the Romans. And Julius Cæsar caused a general survey of the Roman Empire to be made, by a decree of the senate. Three surveyors had this task assigned them, which they completed in 25 years. The Roman itineraries that are still extant, also shew what care and pains they had been at in making surveys in all the different provinces of their empire; and Pliny has filled the 3d, 4th, and 5th books of his Natural History with the Geographical distances that were thus measured. Other maps are also still preserved, known by the name of the Pentingerian Tables, published by Welser and Bertius, which give a good specimen of what Vegetius calls the Itinera Picta, for the better direction of their armies in their march.
The Roman empire had been enlarged to its greatest extent, and all its provinces well known and surveyed, when Ptolomy, about 150 years after Christ, composed his system of Geography. The chief materials he employed in composing this work, were the proportions of the gnomon to its shadow, taken by different astronomers at the times of the equinoxes and solstices; calculations founded on the length of the longest days; the measured or computed distances of the principal roads contained in their surveys and itineraries; and the various reports of travellers and navigators. All these were compared together, and digested into one uniform body or system; and afterwards were translated by him into a new mathematical language, expressing the different degrees of latitude and longitude, after the invention of Hipparchus, which had been neglected for 250 years.
Ptolomy's system of Geography, notwithstanding it was still very imperfect, continued in vogue till the last three or four centuries, within which time the great improvements in astronomy, the many discoveries of new countries by voyagers, and the progress of war and arms, have contributed to bring it to a very considerable degree of perfection; the particulars of which will be found treated under their respective articles in this work.
Among the moderns, the chief authors on the subject of Geography are Johannes de Sacrobosco, or John Hallifax, who wrote a treatise on the sphere; Sebastian Munster, in his Cosmographia Universalis, in 1559; Clavius, on the sphere of Sacrobosco; Piccioli's Geographia et Hydrographia Reformata; Weigelius's Speculum Terræ; De Chales's Geography, in his Mundus Mathematicus; Cellarius's Geography; Cluverius's Introductio in Universam Geographiam; Leibnecht's Elementa Geographiæ generalis; Stevenius's Compendium Geographicum; Wolfius's Geographia, in his Elementa Matheseos; Busching's New System of Geography; Gordon's, Salmon's, and Guthrie's Grammars; and above all, Varenius's Geographia generalis, with Jurin's additions, the most scientific and systematical of any.