《Tetrabiblos》Tropical, Equinoctial, Fixed, And Bicorporeal SignsClaudius Ptolemy（Ashmand 英譯 1822）
These are called _tropical_, because the Sun, after he has arrived at their first points, seems to _turn_, and to change his course towards a contrary latitude;[43] causing summer by the _turn_ he makes in Cancer, and winter by that which he makes in Capricorn.
段落 tetra-1-tropicaleq-3public-domain (Ashmand 1822)
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