3. “Sed ideo aequinoctialis circulus inhabitabilis est, quia sol per medium coelum currens nimium his locis facit fervorem, ita ut nec fruges ibi nascantur propter exustam terram, nec homines propter nimium ardorem habitare permittantur. At contra _septentrionalis et australis circuli sibi conjuncti_ idcirco non habitantur, quia a cursu solis longe positi sunt, nimioque caeli rigore ventorumque gelidis flatibus contabescunt. 4. “Solstitialis vero circulus, qui _in Oriente inter septentrionalem et aestivum_ est collocatus, vel iste qui _in Occidente inter aestivum et australem_ est positus, ideo temperati sunt eo quod ex uno circulo rigorem, ex altero calorem habeant. De quibus Virgilius: “Has inter mediamque duae mortalibus aegris Munere concessae divum. “Sed qui proximi sunt aestivo circulo, ipsi sunt Aethiopes nimio calore perusti.” _De Natura Rerum_, ch. x. [Illustration: FIG. 1] The explanation of the passage and of the figure which illustrates it seems to be that Isidore accepted the terminology of the spherical earth from Hyginus[62] without taking the time to understand it—if indeed he had the ability to do so—and applied it without compunction to the flat earth. He evidently thought that _zona_ and _circulus_ were interchangeable terms,[63] and his “circles” did not run around the circumference of a spherical earth, but lay flat on a flat earth, where they filled with sufficient completeness the _orbis terrae_ or circle of the land.[64] The adjustment of the two conflicting theories was extremely crude, since it involved placing the arctic and antarctic circles side by side, and the two temperate circles one in the east and one in the west. [62] The two passages in which Isidore states the theory of the zones correctly are from Hyginus, _Poeticon Astronomicon_ (_Mythographi Latini_, ed. Muncker, Amsterdam, 1691). _Cf._ p. 146. [63] For a similar confusion of _sphaera_ and _circulus_ see Appendix I. [64] That this was Isidore’s conception of the land surface is evident from many passages (_e.g._, see p. 244) and is made certain from his map (p. 5). This map is found in an old edition of the _Etymologies_ (_Libri Etymologiarum ... et de Summo Bono Libri III_, Venetiis, 1483) in the library of Union Theological Seminary.