Julius Caesar’s attention to science in the midst of his wars and perils is well known.  He first formed the idea of a general survey of the whole empire; and for this purpose obtained a decree of the senate.  The survey was finished by Augustus:  the execution of it was committed to three Greek geographers.  The survey of the eastern portion of the empire was committed to Zenodoxus, who completed it, in fourteen years, five months, and nine days.  The northern division was finished by Theodoras in twenty years, eight months, and ten days:  and the southern division was finished in twenty-five years, one month, and ten days.  This survey, with the supplementary surveys of the new provinces, as they were conquered and added to the empire, formed the basis of the geography of Ptolemy.  It appears from Vegetius, that every governor of a province was furnished with a description of it, in which were given the distance of places, the nature of the roads, the face of the country, the direction of the rivers, &c.:  he adds, that all these were delineated on a map as well as described in writing.  Of this excellent plan for the itineraries and surveys of the Roman empire, from which the ancient geographers obtained their fullest and most accurate information, Julius Caesar was the author.

Julius Caesar certainly added much to geographical knowledge by his conquests of Gaul and Britain:  his information respecting the latter, however, as might be expected, is very erroneous.  Yet, that even its very northern parts were known by name to the Romans soon after his death, is apparent, from this circumstance, that Diodorus Siculus, who died towards the middle of the reign of Augustus, mentions Orkas; which, he says, forms the northern extremity of the island of Britain.  This is the very first mention of any place in Scotland by any writer.

One of the first objects of Augustus, after he had reduced Egypt, was to explore the interior of Africa, either for the purpose of conquest, or to obtain the precious commodities, especially frankincense and aromatics, which he had learned were the produce of those countries.  AElius Gallus was selected by the emperor for this expedition, and he was accompanied by the geographer Strabo; who, however, has not given such accurate information of the route which was pursued as might have been expected.  This is the more to be lamented, as Pliny informs us that the places which were visited during this expedition are not to be found in authors previous to his time.

Gallus was directed by the emperor to explore Ethiopia, the country of the Troglodytae and Arabia.  The expedition against Ethiopia, which Gallus entrusted to Petronius, we shall afterwards examine, confining ourselves at present to the proceedings and progress of Gallus himself.  His own force consisted of 10,000 men, to which were added 500, supplied by Herod, king of the Jews; and 1000 Nabathians from Petra; besides a fleet of eighty ships of war and 130 transports.