Geographical knowledge however was most notably advanced by Strabo, who lived in the Augustan era; although his researches were chiefly confined to the Roman empire.  Strabo was, like Herodotus, a great traveller, and much of his geographical information is the result of his own observations.  It is probable he was much indebted to Eratosthenes, who preceded him by three centuries.  The authorities of Strabo were chiefly Greek, but his work is defective from the imperfect notions which the ancients had of astronomy; so that the determination of the earth’s figure by the measure of latitude and longitude, the essential foundation of geographical description, was unknown.  The enormous strides which all forms of physical science have made since the discovery of America throw all ancient descriptions and investigations into the shade, and Strabo appears at as great disadvantage as Pliny or Ptolemy; yet the work of Strabo, considering his means, and the imperfect knowledge of the earth’s surface and astronomical science in his day, was really a great achievement.  He treats of the form and magnitude of the earth, and devotes eight books to Europe, six to Asia, and one to Africa.  The description of places belongs to Strabo, whose work was accepted as the text-book of the science till the fifteenth century, for in his day the Roman empire had been well surveyed.  He maintained that the earth is spherical, and established the terms longitude and latitude, which Eratosthenes had introduced, and computed the earth to be one hundred and eighty thousand stadia in circumference, and a degree to be five hundred stadia in length, or sixty-two and a-half Roman miles.  His estimates of the length of a degree of latitude were nearly correct; but he made great errors in the degrees of longitude, making the length of the world from east to west too great, which led to the belief in the practicability of a western passage to India.  He also assigned too great length to the Mediterranean, arising from the difficulty of finding the longitude with accuracy.  But it was impossible, with the scientific knowledge of his day, to avoid errors, and we are surprised that he made so few.

Whatever may be said of the accuracy of the great geographer of antiquity, it cannot be denied that he was a man of immense research and learning.  His work in seventeen books is one of the most valuable that have come down from antiquity, both from the discussions which run through it, and the curious facts which can be found nowhere else.  It is scarcely fair to estimate the genius of Strabo by the correctness and extent of his geographical knowledge.  All men are comparatively ignorant in science, because science is confessedly a progressive study.  The great scientific lights of our day may be insignificant, compared with those who are to arise, if profundity and accuracy of knowledge be made the test.  It is the genius of the ancients, their grasp and power of mind, their original labors, which we are to consider.