and of effective changeableness. These considerations are attracting the attention of artistic people, and probably in no other field is there better work being done to-day. It is true that the material is fragile—very fragile—but then few works of art are fashioned with the idea of rough usage. If protected from mere mechanical injury, glass will outlast many forms of matter apparently much more robust. Particularly is it proof against that ever-present enemy, the atmosphere. Stone crumbles and decays, metals corrode, and pigments fade, but glass defies nearly everything but fracture. The few glass ornaments that have come down to us from the ancient world are in a state of superior preservation. Glass and terra-cotta, fragile as they are, seem better adapted than even tablets of stone for preserving the records of the past. Clay cylinders from Assyria, depicting the story of the garden of Eden, are a part of historical record still extant: the graven decalogue is no more.
The subject of picture-windows is a very large one, since their fabrication demands the exercise of such diverse faculties. Viewed from either the artist's or the technologist's standpoint, it presents many features of interest. In our nomenclature we have permitted ourselves to fall into rather careless habits. The terms "painted," "stained," and "mosaic" glass are used indiscriminately to designate any form of window-glass work which involves color, but a moment's consideration will show them to be far from synonymous. Some of our best effects are produced without the use of either paint or stain, and such windows have the advantage of a much greater durability. In painted glass the colors are produced by enamels fused to the surface of the glass by means of heat. In stained glass, a permanent transparent color effect is secured by the action of heat on certain metallic oxides applied to the surface as pigments; while in mosaic glass, pure and simple, the design is brought out by the use of shaped fragments of colored glass bound together by strips of doubly grooved lead.
The three products, it will be seen, are quite distinct. It frequently happens, and in the older examples of ecclesiastical design it is nearly always the case, that all are combined in one window. But at the present time there is a strong reaction against the employment of either paint or stain, since they are not only less durable but also less brilliant than homogeneous colored glass. There is a decided tendency to rely entirely upon the mosaic treatment, and to limit the use of paint to the representation of the human figure.
The manufacture of mosaic glass has attracted the attention of men of such ingenuity and taste that it deserves its rank among the fine arts. It has attained a degree of artistic perfection of