The Romans used lead as a roof covering. In the West “one can hardly (Viollet-le-Duc says) explore the ruins of a Gallo-Roman erection without finding some sheet-lead that had been employed for gutters or roofs.” In the East--Eusebius says of Constantine’s Basilica (the Holy Sepulchre) at Jerusalem--“the roof with its chambers was covered with lead to protect it from the winter rain.” In England Bede tells us of Wilfrid having roofed his church at York with lead in the seventh century, and it has continued without a break in its use as the most perfect of coverings. The methods employed in the middle ages are described by Burges and Viollet-le-Duc. The latter well remarks that of lead covering, as well as many other parts of the construction of buildings, we are a little too apt to think overmuch of the perfection of our modern methods while we are too little careful to learn the experience acquired by our forefathers. The old cast lead is much thicker than the modern milled lead, being as much as twelve or thirteen pounds to the foot of surface. It is certainly not quite even in thickness, and is subject to faults in the casting, but it is not so liable to crack as is milled lead. The old lead employed has also a considerable quantity of silver and arsenic in it, which was the cause of the beautiful white oxide it obtained. Modern lead blackens as the preparation of lead now includes its “de-silverisation.” The acid of timber which has not lost its sap decomposes lead; old building timber was water-seasoned as only ship timber now is. The chief difficulties that had to be overcome in the use of lead were the weight of the sheets of lead to be maintained in position, and the great dilatation of the metal under the heat of the sun, so that it had to be at once strongly attached and free to move. The method followed was to nail it at the top and roll the lateral edges together. The roofing at Canterbury was of twelve-pound lead and about 2.0 between the rolls. The thirteenth century lead of Chartres Cathedral, “covered externally by time with a patina hard, brown, and wrinkled, and shining in the sun,” was in sheets eight feet long, attached at the top by nails with very large heads and held at the bottom by clips of iron that passed down between the sheets and turned over the bottom edge of the upper one. The rolls were formed by turning over the margins one in the other without a wood roll; they were much smaller than the modern ones. Our milled lead is rolled out in sheets about 16 × 6 feet and is usually cut in half lengthways, and 4½ inches is allowed in each edge to form the rolls which are thus 2′-3″ apart. Lead one inch thick is sixty pounds to the square foot, so six-pounds lead is 1/10th of an inch in thickness. We generally make the mistake of putting a longitudinal roll along the ridge, but it is not so done in our old roofs, nor should it be, for the running out of the rolls frets the ridge into a simple decoration.