The masonry is usually of wrought stones squared, but not very neatly put together. M. Mallay, the architect of Clermont, who has restored some of them, ascertained the curious fact that the stone-masons who wrought the stone for the arches, and wherever else superior work was required, marked their stones with the usual mason’s mark, whilst those who wrought the stones for plain walling, jambs, and quoins, made no mark; and he found that precisely the same masons’ marks occurred at Issoire and Notre-Dame-du-Port; whilst the details and plan of Orcival, a few miles south-west of Clermont, are again so identical with both of these, as to leave little room for doubt that it was executed by the same workmen; and I found another evidence of the way in which details were repeated, in some fine ironwork in the south door of Brioude, which occurs again at Orcival. The arches are generally built with small stones of the same size and of even number, so as not to allow of a keystone. M. Mallay says that the mosaic work in the walls of these churches had wide joints of red mortar, projecting from the face of the wall. These mortar joints in the restored work appeared to me to be a bad modern device, and I think that the evidence in their favor ought to be very strong to be convincing. The proportions of these churches are very similar. At Issoire, the width from centre of aisle wall to centre of nave column is one-fourth of the whole width, equal to the width from centre of nave columns, and to the diameter of the chapels in the apse, and one-half the height of the aisle, and one-fourth that of the nave. The height from floor to ridge is equal to the extreme width at base of walls. At Notre-Dame-du-Port the same kind of proportion exists, but from the outside of the buttress to the outside of the nave pier is one-fourth of the whole width.