This, however, was only the beginning of fresh and grave trouble with Charlemagne. The Greeks had annoyed him by cancelling the betrothal of Constantine with his daughter Rotrud, and there is reason to suspect that he already contemplated assuming the title of Emperor. There was, at all events, a sore feeling in France, and when the findings of the Council of Nicæa reached that country, they were treated with disdain and insult. Hadrian had, in his annoyance with the Greeks, refused to give a formal sanction to their findings, but he had so far accepted them as to issue from the Papal chancellery a Latin translation of the _acta_ of the Council. We can readily believe that the translation would be crude and inaccurate, but the quarrel was not based on these fine shades of meaning. The French conception of the use of images differed not only from that of the Greeks, but from that of Hadrian. The northern prelates held that images were to be regarded only as ornaments and as reminders of the saints they represented. In this sense Charlemagne issued, in his own name (though we justly suspect the authorship of Alcuin), the large work which is commonly known as _The Caroline Books_. It scathingly attacked the Greek canons which had been accepted by the Pope; it took no notice of Hadrian's doctrinal letter to the Council; and, in defiance of the familiar Roman custom, it denounced as sinful the practice of burning lights before statues or paying them any kind or degree of worship. It contained assurances of its loyalty to the Apostolic See, but Hadrian must have felt, when at length some version or other of the work was sent to him (three or four years after its publication), that it was an outrage on his spiritual authority. But the book bore the name of Charlemagne, and in his lengthy reply Hadrian prudently concealed his annoyance.[137] In the same year (794) the Frank bishops held a synod at Frankfort and resolutely maintained their position. Whether this synod followed or preceded Hadrian's letter we cannot say, but the Franks continued for years to reject the Roman doctrine.[138]