After the bronze age comes the iron age. The introduction of iron wrought a great change in metalworking, but, as iron is a metal very subject to oxidization, comparatively few early iron remains are found. There are some swords of an early pattern in the National Museum at Dublin. It has been shown that the pre-Christian metalwork of Ireland is well worthy of attention, but it is to the early Christian metalworkers that Ireland owes her pre-eminent fame in this field. In early Christian Ireland metalworking was brought to a pitch rarely equalled and never excelled. The remains found, such as the Tara Brooch, the Cross of Cong, and the Ardagh Chalice, are among the most beautiful metalwork in the world. The wonderful interlaced patterns, which are typically Celtic, bewildering in their intricacy, and fascinating in the freedom and boldness of their execution, lend themselves readily to metal work. The connecting link between the metalwork of the late pagan period and that of early Christian times is chiefly exemplified by the penannular brooches, of which great numbers have been found in Ireland. Examples of this characteristically Celtic ornament may be seen in all Celtic countries. In its earliest form this brooch is simply a ring, with a gap in it, to which a pin is loosely attached by a smaller ring. Gradually the open ends of the ring, which need some enlargement in order to prevent the pin slipping off, became larger and ornamented. In time these became regular trumpet-shaped ends, generally ornamented with characteristic "trumpet" patterns. The next stage was to close the gap, leaving a ring with a crescent-shaped disc at one side. Space does not permit of the description of the numerous brooches found. It will be sufficient to describe the Tara Brooch, which is the crowning glory not only of the Irish but of any metalworker's art. The Tara Brooch, whose only connection with Tara is its name, was found near Drogheda; it is about seven inches in diameter and the pin about fifteen inches long. It is made of bronze covered with the most elaborate interlaced ornament in gold. The fineness of the interlaced work may be compared with, and is quite equal to, that of the best illuminated manuscripts; the freedom of its execution is amazing. Besides panels of ribbon ornament, which include spirals, plaited work, human heads, and animal forms, the front of the brooch is decorated with enamel and settings of amber and colored glass. The back of the brooch is, as is often the case in Irish work, decorated in a bolder manner than the front, and the "trumpet" pattern is there very marked. The head of the pin is also elaborately decorated. The minute and intricate style of the work is strikingly shown by the fact that, even after prolonged study, some patterns escaped notice and have only lately been discovered. Further, each of the gold lines is made of tiny gold balls, so small as only to be seen by means of a magnifying glass.