The stone used in the erection of the Cathedral was brought from Barnack, near Stamford, and is of a much harder nature than what was commonly used; it gives proof of great soundness and durability in the excellent preservation of some of the mouldings. The soft white stone used for some of the interior decorations is called "clunch," and is found within a few miles of Ely; it is well adapted for the purposes to which it is applied, it is easily worked and capable of being highly finished, but will not bear exposure to the weather. Most of the pillars with their capitals and bases, as well as many of the mouldings and ornaments in the Early English portion of the church, are of Purbeck marble. The lower portions both of the Tower and wings were built by Bishop Ridel (1174-1189), and completed as high as the first battlements, during the episcopate of his successor, Longchamp (1189-1197), who however, spent none of his money on the fabric; the lower part of this work is late Norman, but the upper portions show indications of transition towards the pointed style. The architecture of the Tower is worthy of attention, as it shews some beautiful specimens of arcading in bands between rows of windows, all enriched with mouldings of various kinds; the western face shows three rows of windows, the others but two, as the lower one would have been hidden by the roof of the nave and of the wing on each side, these last being originally of a higher pitch than the remaining one now is. The upper band consists of circular openings with quatrefoils in the centre, and above that is a corbel-table. A spire of timber covered with lead was erected on the Tower about the middle of the thirteenth century, but it was afterwards removed, and the upper portion of the Tower, in the Decorated style, was added, and it was again surmounted by a spire. These additions were found to be injurious, and it became necessary to strengthen the lower portions of the Tower to support it; nor is it improbable that the fall of the north-western Transept was in some degree owing to the great additional weight, or that it was so far injured as to require removal. The spire was, we believe, finally removed about the end of the last century. The octagonal story does not harmonize with the lower portion. There is a large window with transoms in each of the four principal sides, the upper portions only being glazed; it is flanked by octagonal turrets, which rise a little higher than the centre, they are faced with shallow arcading and connected with the centre portion by small flying buttresses; in each turret is a winding stair, but only that in the south-eastern turret is used. In the top of this turret is placed the clock bell.