The curious "stone beam," about which so much has been conjectured, and so little is known, is constructed between the walls of the two western towers, just above the stone vault of the nave. It is really an arch of very slight curvature, composed of twenty-three stones of unequal length, but of uniform depth and breadth. Examination has proved that there is nothing but mortar in the joints, and there are no traces of iron having been used in the construction. When jumped upon, the "beam" vibrates appreciably. It has been suggested that it was constructed in order to try whether the towers were capable of supporting the additional weight of upper storeys, but nothing appears to be satisfactorily known as to the purpose it served or the date of its erection. The =Nave= was constructed, together with the two chapels at its western end, during the first half of the thirteenth century. Attempts have been made to distinguish earlier and later features in different parts. For example, the morning chapel on the north side is considered to be somewhat earlier than the consistory court opposite to it; but there being no documentary evidence to guide us, all that we may safely say is, that the nave is later than the time of St. Hugh (d. 1200), and was practically completed before the death of Bishop Grosseteste, which occurred in 1253. Taken as a whole, it is one of the best examples of the Early English style we possess. The late Sir G. G. Scott, in his lectures on Mediæval Architecture, thus speaks of it--"It exhibits an Early English style in its highest stage of development: massive without heaviness, rich in detail without exuberance, its parts symmetrically proportioned and carefully studied throughout, the foliated carving bold and effective, there seems no deficiency in any way to deteriorate from its merits." In dignity especially, the eminent architect considered the nave to be superior to all other parts of the cathedral. [Illustration: THE NAVE, LOOKING WEST. _Photochrom Co. Ltd., Photo._]