The windows of these churches, which have nearly always pointed arch-heads, are necessarily placed at a low level, so as to allow the point of the arch-head to come beneath the spring of the main vault. This is done so as to avoid even a small groin, such as would be required if the window arch-head were carried up into the main vault. The object is two-fold--first, to escape the difficulty of the intersection of the vaults; and second, to avoid the small gablets over the windows and the small stone roofs and valleys which would be required at the junction of these with the main external stone roofs. The above features are all well exemplified at Ladykirk, Seton College, Corstorphine, and many other churches. It should be borne in mind that the vaulting in England in the fifteenth and sixteenth centuries had also to some extent reverted to the plan of relying chiefly for strength on plain surface vaulting, and not on the ribs as in the earlier period. The example from Winchester Cathedral[5] helps to explain this. The intersection of the vaults is there very slight, and the numerous ribs introduced are almost all used ornamentally. This is also the case in the fan vaulting, so common in England in the fifteenth and sixteenth centuries, in which the ribs or tracery are applied as ornaments on the surface of the vaults. Ornamental ribs are not uncommon in Scottish roofs. An early example, somewhat similar to that at Winchester, still exists over the presbytery of Melrose Abbey, where the intersection of the vaults is almost entirely abandoned, and numerous ornamental surface ribs are introduced. In later examples, however, the intersection of the vaults is completely given up, and any ribs employed are useless except as ornaments. Such are the roofs of St. Mirren’s Chapel, Paisley, and the choir of Seton College. An example of the shifts the builders were put to in order to escape intersecting vaults may be seen in the apse of Stirling Church. In other examples, such as Dunglass and Queensferry, the nave, choir, and transepts have walls carried up on the four sides of the crossing, against which the pointed barrel vaults are stopped, and access is furnished to the various arms of the church by small archways like doorways in the walls. At Whitekirk the crossing is exceptional, having a groined vault; but the choir, &c., have pointed barrel vaults, which stop upon walls at the crossing. In the case of the apse of Linlithgow Church the difficulty of the intersection of the apse with the choir vault was avoided by sticking on the apse against the east end wall, like a large bow window. This enabled the apse windows to be carried to a good height. Generally speaking the windows in the apse are very low, being kept down below the main arch, and admit little light, thus rendering the vault extremely dark, as, for instance, at Seton Church.