Between the four great piers of the west front there are now three doorways. If, however, we refer to the plates of Salzenberg, we shall find that only the two lateral ones are there shown, and that the position of the central door is occupied by a window; this arrangement was seen by Texier in 1834, and is shown in a MS. drawing of his, now in the library of the Royal Institute of Architects. Referring to the views and plan which Grelot published in 1680, we see the central bay occupied by a belfry, with a pyramidal top rising above the roof of the exonarthex. Now in Goar’s _Euchologium_[323] there is a note to this effect, “The Greeks first took up the use of bells from the time when Urso Patricio, Doge of Venice, in the year 865, sent them to Michael the emperor, who greatly valued them, and built a tower for them against S. Sophia.” We have already seen that large repairs were made to the west front of the church about this time (page 123), with a view of counteracting the thrust of the vaults. Before the belfry was built the Semantron would have been used; this was a plate of bronze or wood suspended in the atrium and struck like a gong (see Fig. 28). It appears from the Russian pilgrims that the bells remained in use for only a short time. A sixteenth century French MS. in the British Museum speaks of the old square tower and bells. Grelot[324] says “this tower, formerly the belfry, is now void, the Turks having exchanged the music of bells for the noise of cannon.” It was not fifty _toises_ high, and could not have held many bells, or large ones.[325] [Illustration: FIG. 28.--Semantron at Constantinople, from Lenoir.] The upper story of the narthex, Grelot tells us was supported by six flying buttresses, and both his exterior views show three complete piers and flying arches on each side of the tower. The bay next the belfry on the right was occupied by a low building with a pent roof, in which were descending steps, at the bottom of which they drew off water from “the great cisterns under the church, from which it was said a boat might reach the sea.” As to the doors there were three towards the west, used when Grelot made his plan, two being those at the extreme north and south, opposite the lateral atrium walks, and the other, which was less, and little used, was next the belfry on the left, and is in fact the left one of the three present doors. The arches, which cover two of the spaces between the piers and make them into porches, are shown in the view by Fossati of the unrestored state of the front. [Illustration: FIG. 29.--West Front as altered in the Ninth Century.]