The first six books of the great encyclopaedia compiled by Pliny the elder (A.D. 23-79)[341] contain an account of the universe and the earth, which is of the greatest value, and was long exploited by compilers of later times, among the earliest and best of whom was Solinus.[342] Equally famous with Solinus was the author of a work of more independent character, Pomponius Mela, who lived in the first century A.D. His geography, commonly known as _De situ orbis_ from the mediæval title, though the proper name is _De chorographia_, is a work of importance and merit. In the Middle Ages it had wonderful popularity.[343] Cicero, who contemplated writing a history of geography, touches upon the arrangement of the earth’s surface several times in his works, as in the _Tusculan Disputations_, and notably in the sixth book of the _Republic_, in the episode known as the “Dream of Scipio.” The importance of this piece is enhanced by the commentary upon it written by Macrobius in the fifth century A.D.[344] A peculiar interest attaches to the poems of Avienus, of the fourth century A.D., in that they give much information about the character attributed to the Atlantic Ocean.[345] The astronomical poems of Manilius[346] and Hyginus were favorites in early Middle Ages. The astrological character of the work of Manilius made it popular, but it conveyed also the true doctrine of the form of the earth. The curious work of Marcianus Capella gave a résumé of science in the first half of the fifth century A.D., and had a like popularity as a school-book and house-book which also helped maintain the truth.[347] Such in the main are the ancient writers upon which we must chiefly rely in considering the present question. In the interpretation of these sources much has been done by the leading modern writers on the condition of science in ancient times; like Bunbury, Ukert, Forbiger, St. Martin, and Peschel on geography;[348] like Zeller on philosophy, not to name many others;[349] and like Lewis and Martin on astronomy;[350] but there is no occasion to go to much length in the enumeration of this class of books. The reader is referred to the examination of the literature of special points of the geographical studies of the ancients to the notes following this Essay. * * * * *