These twenty-four hymns by Luther were followed in after years by only twelve more from his own pen, among the latter being his grand hymn, _Ein' feste Burg ist unser Gott_, written probably in 1527. Of these later compositions, comparatively few expressed entirely his own ideas; most of them had reference to subjects already in the possession and use of the Christian world, and of German Christians in particular; that is to say, some referred to the Psalms and other portions of the Bible, others to parts of the Catechism, others again to short German ballads, sung by the people, and even to old Latin hymns. In all of them he was governed by a strict regard to what was both purely evangelical, and also suitable for the common worship of God. And yet they differ widely, one from another, in the poetical form and manner in which he now gives utterance to the longings of the heart for God, now seeks to clothe in verse suited for congregational singing words of belief and doctrine, now keeps closely to his immediate subject, now vents his emotions freely in Christian sentiments and poetical form, as for example in _Ein' feste Burg_, the most sublime and powerful production of them all. The new hymns went forth in town and country, in churches and homes, throughout the land. Often, far more than any sermons could have done, they brought home to ears and hearts the Word of evangelical truth. They became weapons of war, as well as means of edification and comfort. In his preface to a small collection of songs, which Luther had published in the same year, he remarks: 'I am not of opinion that the gospel should be employed to strike down and destroy all the arts, as certain high ecclesiastics would have it. I would rather that all the arts, and especially music, should be employed in the service of Him who has created them and given them to man.' What he says here about music and poetry, he applied equally to all departments of knowledge. He saw art and learning now menaced by wrong-minded enthusiasts. For this reason he was particularly anxious that they should be cultivated in the schools. With great zeal he directed his counsels to the general duty of caring for the good education and instruction of the young, as indeed he had done some time before in his address to the German Nobility. These, above all, he said, must be rescued from the clutches of Satan. He had again in his mind schools for girls. Thus in 1523 he recommended the conversion of the cloisters of the Mendicant Orders into schools 'for boys and girls.' The same advice was offered by Eberlin, already mentioned, who was then living at Wittenberg, and who made the suggestion to the magistrates of Ulm.