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Meanwhile a party in Sicily had chosen Tancred, an illegitimate son of Roger, son of King Roger II., as their king, and he had already won considerable authority and was favoured by the pope.

It is, however, with the beautiful chapel built by Roger II. in the early part of the twelfth century that we are concerned.

Idrisi, the best known of the Arabian geographical authors, after travelling far and wide in the first half of the 12th century, settled in Sicily, where he wrote a treatise descriptive of an armillary sphere which he had constructed for Roger II., the Norman king, and in this work he incorporated all accessible results of contemporary travel.

The rival of the latter, Anaclete II., was supported by the Norman king, Roger II. of Sicily, who, in the summer of 1137, was driven out of Southern Italy by Lothar's army.

The Zeirids were finally overthrown by Roger II. of Sicily in 1148.