Hope, the author of an historical Essay on Architecture, had a keen prevision of this guild, although he had no documents or archives, but only the testimony of old stones and buildings to prove it. After sketching the formation of the Roman _Collegia_, and the employment of their members as Christian architects under the early Popes, he says "that a number of these, finding their work in Rome gone in the times of invasion, banded together to do such work in other parts of the world." He seems to think that the nucleus of this union was Lombardy, where the superiority of the architecture, under the Lombard kings, was such that the term _Magistri Comacini_ became almost a generic name for architects. He says that builders and sculptors formed a single grand fraternity, whose scope was to find work outside Italy. Indeed distance and obstacles were nothing to them; they travelled to England under Augustine, to Germany with St. Boniface, to France with Charlemagne, and again to Germany with their brother _magister_, Albertus Magnus; they went to the east under the Eastern Emperors, to the south under the Lombard Dukes, and in fact are found everywhere through many centuries. The Popes, one after another, gave them privileges. Indeed the builders may be considered an army of artisans working in the interest of the Popes, in all places where the missionaries who preceded them had prepared the ground for them. [Illustration: CHURCH OF STA. COSTANZA, ROME. BUILT IN THE 4TH CENTURY. (_From a photograph by Alinari._) _See page 11._]