In fact, our ignorance on this point affords an excellent example of a difficulty that is met with again and again in this history of ours,—the difficulty, I mean, of controlling our literary material by means of the scanty examples of glass that have come down to us. It would require a large shelf in a library to hold all the bulky volumes dealing with the history of French glass that have of late years been published, works that are due above all to the local patriotism and the industry of provincial investigators. For books of this kind, the fashion was set as long ago as 1864 by M. Benjamin Fillon in his _L’Art du Verre chez les Poitevins_. Since then have appeared not mere _brochures_, but in many cases portly volumes tracing the history of the manufacture in Normandy, Picardy, Lorraine, Nevers, Lyons, and Provence. M. Schuermans has devoted to France a long letter, chiefly concerned with the settlements of Altarist workmen (_op. cit._, vol. xxxi.). And yet not only are specimens of glass, undoubtedly French, of the sixteenth and seventeenth centuries comparatively rare, but in very few cases can anything more than a guess be made as to the provinces to which these specimens are to be attributed. Such attributions indeed, when attempted, have for the most part had to be based either upon the armorial bearings forming part of the enamelled decoration, or again upon the localities where the glasses have been found—and these are criteria that fail in most cases. Among the many anomalies that we encounter in the course of this inquiry—and surely in no kindred branch of art history are so many met with—there is nothing more surprising than the numerous important ‘developments’ of glass of one kind or another, for which we may search in vain a rational explanation—unless, indeed, it is the corresponding fact of the unexplained barrenness of certain periods and countries where such poverty would have been the least expected. One source of this apparent caprice in the presence or absence of glass of artistic merit at times and at places where the contrary might have been looked for, may be found, perhaps, in the fact that although, since Roman days at all events, the making of glass has always been an important industry, it is an industry that has only incidentally come into connection with the æsthetic movements of the time.[166] Some such explanation may perhaps be given for the comparatively subordinate place taken by France in the history of artistic glass, at least until quite recent days. In one department of the vitreous arts the French occupied no doubt for a time the premier place—the stained glass of their cathedrals is acknowledged to be the finest in Europe. But in our branch of the manufacture, a branch for which, curiously enough, the French alone have provided a name—_la verrerie_—that nation has never occupied a prominent position. Since Roman times, the first place as