The former must certainly have been the case wherever the incrustation did not extend over the whole surface of the walls, which was very frequently the case; but the latter is not really a fault; it was only an elaboration in a more beautiful material of the same system which we have seen pursued with such happy results by the builders of Verona in brick and stone,[102] and which we find adopted by the architects of Northern Germany in the frequent alternation of courses of red and black brick, and sometimes by our own forefathers in the coursing of flint work with stone, or in the counterchanging of red and white stones which we see in some of the Northamptonshire churches. The system was a thoroughly sound one, because it not only proceeded from and depended on the natural arrangement of the material, but afforded the best possible means for displaying the various colours which were to be used. Probably all these systems are mainly useful now as shewing us certain principles which we may work out and apply to our own somewhat different circumstances; and surely one of our first objects ought to be the discovery of the extent of our means and opportunities, which in this matter are at the present day far beyond what is generally imagined. It must never be forgotten by us that our forefathers had very limited means of obtaining materials from one locality and transporting them to another; and were moreover, to a great extent, unacquainted with the materials which might, if necessary, be obtained. We have not this excuse; we not only know what materials we may obtain, but we have at the same time marvellous facilities for their conveyance between all parts of the country; and we know also how much has been done of old in other countries by using them in a proper way. No excuse therefore can be found for us if we continue to neglect to avail ourselves of them as though they were still undiscovered. We have alabaster, which may be wrought at a really trifling expense; large fields of marbles, of which those of Devonshire and Ireland are particularly valuable for architectural decoration, and those of Derbyshire and Purbeck for the formation of shafts and columns: we have, moreover, an exhaustless supply of granites of various colours; of serpentine; and, lastly, of building-stones of many tints, many of which may be very effective when contrasted. In addition to these natural materials we have every facility for making the most perfect bricks; and, owing to the excellence already achieved by our manufacturers of glass and pottery, we have no difficulty in making mosaics and tiles, either for roofing, flooring, or inlaying, of any degree of beauty, either of colour or form.