Page:Popular Science Monthly Volume 16.djvu/511

Rh care the works of his predecessors, collected all the information that was procurable from travelers and mariners, and produced a geographical work far beyond anything that had preceded it, illustrated by maps which were covered with a network of parallel and meridian lines, cutting each other at right angles, under which the different places were indicated according to their direction and distance from each other. His object was to put an end to the uncertainty about the position of countries and cities, by assigning to every locality or place its approximate latitude and longitude. He divided the globe into sections, each having an astronomical extent of fifteen degrees, and the places falling within these limits he put together in what he supposed to be their relative position to each other. He drew a line due east from the Fortunate Islands, and arranged countries and places in what he regarded as their proper position north and south of this line, so as to bring them alike under the proper zone or climate, as well as under the astronomical section he had devised.

Marinus was probably the first who undertook to combine systematically the results of astronomical observations with those of travelers and mariners in determining geographical positions. There being no delicate instruments to-indicate direction, altitude, or time, the latitudes and longitudes ascertained were at first, of course, erroneous. Marinus corrected earlier errors, and accumulated much new material for the preparation of a geographical work which premature death prevented him from perfecting.

The geography of his immediate successor, Ptolemy, which has fortunately come down to us, was written at least within half a century afterward, and, as Ptolemy himself says, was based upon the work of Marinus.

Ptolemy's labor was what in this day we should call editing a new and revised edition of an existing work. Ptolemy was a much better mathematician and astronomer, but evidently very inferior as a geographer to his predecessor. He undertook to correct Marinus's chief error by reducing his projection of the earth, from east to west, from 225° to 180°. In making this geometrical correction, however, he fell into a multitude of errors which, had he been a better geographer, he would readily have detected.

A period of twelve hundred years elapses from the time of Ptolemy to the inauguration, by Prince Henry the Navigator, of Portugal, of the spirit of maritime enterprise which led to the circumnavigation of Africa, and the discovery of the Continent of America. This long interval is marked by the decline in Europe of everything in the form of geographical knowledge, until a state of ignorance was reached in which little interest was felt in any branch of human learning. For the purposes of our inquiry it may be divided into three periods. The first was one of long-continued and nearly incessant wars, during which