The plain surfaces of the walls in Venetian work were commonly either entirely inlaid, or else inlaid within a square inclosing border of projecting moulding. The inlaying was composed of a number of rectangular slabs of marble, not by any means always of the same size, supported to some extent by the projections of the inclosing marbles or by those of the archivolt, but always dependent mainly on metal cramps let into the fabric of the wall; and, when possible, these marbles were slabs cut out of the same block, and put side by side, so as to produce a kind of regular pattern wherever the veining of the marble was at all positively marked. The other mode of introducing constructional colour in marble commends itself to one’s reason as that which is most likely to endure for ages, and as that, therefore, which ought, wherever it may be, to be adopted. The first idea of the architects of these buildings seems to have been to arrange their material with as much regard to strong contrasts of colour as was possible. The first thing they did, therefore, was to alternate the colours of every course of masonry, either simply as in the Broletto at Como[100] and in Sta. Maria Maggiore at Bergamo,[101] or as in the west front of the cathedral at Cremona, where very narrow layers of white marble are laid between each of the other courses, which are of course so much the more defined. The description which I have already given of these works, as well as of the porch at Bergamo, will shew how regular is the way in which this system of counterchanging the colours was carried out by the purely constructional school; this is, in fact, the great mark of difference between the constructional and the incrusting school of Italian architects, the whole arrangement of coloured materials by the two schools being quite different, and producing singularly different results. The most common fault of the Venetian system of incrustation must have been that upon a general surface of plain wall you had here and there a square patch of marble surrounding a window opening; that of the other system would be, in the opinion of many, that you have too stripy an effect of colour, and that all the divisions, moreover, are horizontal.