To take but a single example, it will be readily appreciated that the consideration of the guilds of builders of the Cathedrals as constituting a great technical school, is marvelously emphasized by certain recent observations with regard to architects' and builders' methods in the Cathedrals. There is a passage in Evelyn's Diary in which he describes certain corrections that were introduced into Old St. Paul's Cathedral, London (the Gothic edifice predecessor of the present classical structure), in order to remove appearances of dissymmetry and certain seeming mistakes of construction. This passage was always so misunderstood that editors usually considered it to be defective in some way and as the classical critics always fall back on an imperfect text for insoluble difficulties, so somehow Evelyn was considered as either not having understood what he intended to say, or else the printer failed to put in all the words that he wrote. It was the modern readers, however, not Evelyn nor his printer who were mistaken. Mr. Goodyear of the Brooklyn Institute of Arts and Sciences has proved by a series of photographs and carefully made observations, that many of the old Gothic Cathedrals have incorporated into them by their builders, optical corrections which correspond to those made by the Greeks in their building in the classical period, which have been the subject of so much admiration to the moderns. The medieval architects and builders knew nothing of these classical architectural refinements. They learned for themselves by actual experience the necessity for making such optical {132} corrections and then introduced them so carefully, that it is not until the last decade or so that their presence has been realized. It is only by an educational tradition of the greatest value that the use of such a refinement could become as general as Professor Goodyear has found it to be. Besides the practical work then, and the actual exercise of craftsmanship and of design which the apprentices obtained from the guild, there was evidently a body of very definite technical information conveyed to them, or at least to certain chosen spirits among them, which carried on precious traditions from place to place. This same state of affairs must of course have existed with regard to stained glass work, the making of bells and especially the finer work in the precious metals. Practical metallurgy must have been studied quite as faithfully as in any modern technical school, at least so far as its practical purposes and application were concerned. Here we have the secret of the technical schools revealed.