Within the _oikoumene_ the phenomena resulting from varying elevations of the ecliptic in different latitudes were fairly well understood. The facts that there are two summers between the tropics (particularly in India) and that the sun there passes vertically overhead twice a year had been commented on by Pliny and Solinus, whose observations in this connection found their way into Isidore’s _Etymologiae_[1095] and thus to the works of the plagiarists of Isidore in our period. The _De imagine mundi_,[1096] the _Image du monde_,[1097] Gervase of Tilbury,[1098] and John of Holywood[1099] all tell us that the same phenomenon was said to occur in Arabia which lies between the tropics. Similarly the long days and nights of far northern latitudes were described on the authority of Solinus and Isidore. In the _De imagine mundi_,[1100] from which Gervase copies, it is said that in the island of “Chili” (Thule) there are six months of daylight and summer and six of night and winter. Giraldus Cambrensis also quotes Solinus[1101] and Isidore[1102] to the same effect and adds a brief description of how the sun continuously circles around the horizon during the long Arctic day and how its light disappears completely when the luminary departs southward towards the Tropic of Capricorn.[1103] “CLIMATA” The ancient geographers had divided the earth’s surface into _climata_, or climates, which, as we have already seen,[1104] were not atmospheric regions but mathematical strips running east and west and bounded by parallels of latitude. Pliny,[1105] for instance, had conceived of seven climates, the first in the latitude of India, where the length of the longest day is fourteen hours, and the seventh in that of the Borysthenes (Dnieper) and of Venetia, Umbria, Milan, and Aquitania, where the longest day is fifteen and three-quarters hours. Martianus Capella[1106] added an eighth climate in the north between the parallel of the Borysthenes and that of the Rhipaean Mountains. Furthermore, he applied names to the strips. It must be added, however, that neither Pliny nor Capella were precise in the data they gave, and neither indicated in degrees the latitude of the parallels which bound their climates. More definite is the information we find in the two works of Ptolemy. The _Almagest_[1107] and _Geography_[1108] give accounts of the characteristic astronomical phenomena that occur along a series of parallels, thirty-eight in number according to the former, twenty-one according to the latter.[1109] The positions of these were determined by the length of the longest day at each one. Though there is no explicit mention of the older division by climates in the text of either of Ptolemy’s books, such a division not only appears upon the map of the world made by Agathodaemon on the basis of material supplied by Ptolemy but also upon certain of the special regional maps which were probably the work of Ptolemy himself.[1110]