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view with considerable indulgence a weakness whichproduced substantial benefits to science.

The emperor Frederic II . was a prince distinguishedas well by a very cultivated mind, as by a liberal patron-age of learned men. To his encouragement we owe thefirst translation of Ptolemy’s great work into Latin fromthe Arabic (Greek being as yet unknown in Europe ) ;but the Arabic translation was far from being faithfulto the original, and the work (executed by Gerard ofCremona ) was consequently very faulty,; yet it was ofimportance for promoting the knowledge of astronomyin that age.

To Alphonso X., king of Castile , science owes stillmore than to Frederic. His situation in a country bor-dering on that of the Arabs , who then occupied thesouth of Spain , was favourable for collecting about himable astronomers, who were then only to be found in theMoorish universities. He employed many of theselearned persons in the elaborate construction of aset of astronomical tables, which were to be enrichedwith the observations of the centuries since Ptolemy .(a. d. 1250.) Notwithstanding the zeal and muni-ficence of the king, however, these tables do not appearto have realised his design. One of their worst faultswas the introduction of a peculiar inequality in themotion of the fixed stars in longitude, which had atthat time obtained credit, and was called the trepidation.It was made out as a theoretical consequence from apeculiar motion in the eighth sphere of Ptolemy ’s system.It was for some reasons strenuously maintained as ofhigh importance by the Arabian astronomers, thoughnot recognised by Ptolemy himself; and was connectedby the Jewish astronomers or astrologers with certaincabalistical mysteries. It had not, however, the smallestfoundation in any thing actually observed.

Of Alphonso ’s own attainments in science we haveno precise indications ; but his often quoted remark onthe complexity of the Ptolemaic system certainly indi-cates a mind superior to the prejudices of his age.

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