By this careful observer it has been shown that a couch of sandy mortar was first laid on the stones of the vault, then a second layer, rich in lime, and especially in white of egg, was applied, and the surface was ready for the application of the colours. These are blue, green, yellow ochre, reddish-brown, black, and white. Cobalt blue, or "azure," was only discovered in the sixteenth century by a German glass-maker. The blue used in these paintings is the true "outremer" of the twelfth century, the solid colour made from lapislazuli, which was worth its weight in gold. That it was employed at all, is one more evidence of the munificence of Henry II. in his foundation. The green is a mixture of this blue with the yellow ochre. The white was made of powdered egg shells, and the black is lamp black. From the fact that the colouring matter has in no case penetrated the prepared surface, but adheres to it, we may argue finally that the process in which white of egg is the chief constituent was used to lay on the colours. Besides the heart of Richard Coeur de Lion, the Cathedral of Rouen contains another relic of the Norman days in the tomb of that Empress Matilda, who as Countess of Anjou, gave Henry Plantagenet to the throne of England, and died in 1167. Her rich sepulchre at Bec was pillaged by the English in 1421, and the restored monument was desecrated in 1793, but in 1846 the original casket was discovered by the fortunate stroke of a pickaxe, and now rests in the Cathedral. In 1124 the shrine containing the body of the famous St. Romain was opened in the presence of the King and Queen of England, and fifty-four years afterwards, as the decorations made for it by Guillaume Bonne Ame had been taken for alms to the poor, Archbishop Rotrou made a new and more magnificent covering for the venerated relics that play so large a part in the story of the town. This new and Norman shrine it must have been which was carried by the two prisoners, delivered by the Privilege of the Fierte in 1194, but it has long ago been replaced by later work. [Illustration: CORBEL FROM THE OLD CHURCH OF ST. PAUL] There is but one more religious monument, the last building I can show you in this chapter, that has remained from these centuries until now. Walk along the riverside eastwards, and as the waters flow from Paris towards you on your right, stop where the chalk cliffs of St. Catherine's Mount begin to slope downwards from the left hand of the road. Just between it and the river is the Church of St. Paul, which stands where the first Christian altar replaced the Temple of Adonis, and watched with St. Gervais and St. Godard the infant town of Rothomagus arise.