Meanwhile, the northern climate demanded the additional light provided by a clerestory, and the architects of Normandy applied themselves to the problem. It was to be solved later in Gothic architecture by the use of pointed groin vaulting, but, pending this discovery, a method of vaulting was employed which is known as sexpartite. For the square bay was crossed in the centre by another transverse arch, which, when cut by the two diagonals, produced a plan of six parts. This, however, necessitated two narrow skew vaults, meeting in the centre, which was awkward in appearance. The method is illustrated in =S. Etienne=, the great church of the =Abbaye-aux-hommes= and =La Trinité= of the =Abbaye-aux-Dames=, both in =Caen=. These and other churches of Normandy such as the Abbey church of =Mont-St. Michel=, are characterised by an adventurous spirit as well as logic of design, marking a distinct progress toward the Gothic. ENGLISH ROMANESQUE OR NORMAN The audacity and resourcefulness of the Norman builders found extensive opportunity after the conquest of England. But few remains survive of Anglo-Saxon architecture, and they suggest that the buildings were of a rude kind. They were constructed of rubble work, reinforced with engaged piers and ashlar masonry at the corners, arranged in what is called “long and short” courses. The columns were short, stumpy cylinders crowned with one or two square blocks, and the details of doorways and windows were roughly hewn with an axe, though in the case of certain belfry windows, jambs of baluster shape, seem to have been turned upon a lathe. The openings were either round-topped, suggesting a clumsy copy of the Roman style or else triangular, as if perpetuating a form of timber construction. The plan of the church appears to have been of the simplest, representing an oblong nave, separated by an arch from the smaller oblong of the chancel; the latter being lower than the nave and, on the inside, approached by two or three descending steps. The arrangement seems to have been derived from the example of the Celtic churches, as also was the habit of erecting towers, which, however, are not circular as in Ireland, but square without buttresses. One example of such a tower exists at =Earl’s Barton=, =Northamptonshire=, in which occur balustered windows. The Normans, therefore, had a free field for their architectural enterprise and, while they immediately commenced the erection of castles to overawe the country, they also erected monasteries and cathedrals, designed to surpass in size and magnificence the ones in Normandy. While following the latter in a general way, the English examples were characterised, on the one hand, by a more massive and picturesque treatment, and, on the other, owing probably to the scarcity of skilled labour, by simpler and less refined details.