Little difference in shape is traceable in the mitres of the thirteenth, fourteenth, fifteenth or sixteenth centuries. During these four hundred years the mitre increased considerably in size, but it was reserved for the seventeenth century to stereotype the final modification in form. Hitherto the two horns of the mitre had as a general rule been in the shape of plain triangles, bent round so as to adapt themselves to the outline of the head; the mitre was thus cylindrical in outline. By the seventeenth century, however, the triangles had been made spherical, so that the mitre assumed the form of a pair of parentheses, or of a barrel, which it still possesses.[70] By this time it had grown to a considerable height—some eighteen inches. When the mitre was a plain cloth cap it was kept in position by two ribbons, which were knotted at the back of the head. The end of these ribbons are well shown in the figure of St Dunstan. But the ribbons very early lost their usefulness and became simple ornaments, and the ubiquitous embroiderer was not long in seizing on these _infulae_, or lappets, and enriching them with needlework to the best of her ability. The mitre was originally made of plain white linen, and until about the twelfth century continued to be so; it was occasionally, though by no means always, elaborately decorated with needlework. Such simplicity, however, was not consistent with the spirit of the age which followed, and we find that in the thirteenth century the mitre was made of silk, and invariably overlaid either with embroidery or pearls and other jewels. To such a length was this enrichment carried at last in England, that we read that Henry VIII removed from Fountains Abbey, among other treasures, a silver-gilt mitre set with pearl and stone—weight seventy ounces! Although properly belonging to the seventh chapter, in which the ritual uses of the various vestments which we have been describing will be discussed, it is necessary here to detail the three classes into which mitres are divided. Unlike other vestments, which are classified according to the particular liturgical _colour_ which predominates in their embroidery, mitres are classified according to the _manner_ in which they are ornamented. The background, when it can be seen at all, is white. A mitre which is simply made of white linen or silk, with little or no enrichment, is called a _mitra simplex_; one ornamented richly with embroidery, but without precious metals or stones, is called a _mitra aurifrigiata_; and one in which precious metals and stones are employed in its decoration is called a _mitra pretiosa_. The different times at which these different kinds of mitres are worn will be noted in their proper place in Chapter VII. [Illustration: FIG. 18.—PASTORAL STAFF AND MITRA PRETIOSA (the Limerick Mitre).]