chapels, built much later. Now as to the forest of flying buttresses, those sloping bars of stone carried on stone arches, which surround the clearstory, the only purpose of these is to receive and neutralize the thrust of the vaults within. The high vault above the clearstory pushes against the uppermost flying buttresses. The vault of the inner aisle has its much less formidable thrust taken up by the vaults of the outer aisle as far as the lines of the plan are straight, east and west, and by those of the chapels as soon as the curve of the chevet[42] begins. By means of the double set of flying buttresses, those within and higher and the outer and lower ones, the thrust of the high vaults is carried across the whole space occupied by the two aisles, and finally turned over to the upright piers which themselves serve also as buttresses for the outer aisle. Or, to approach the same set of counteracting forces from without, we have as we walk along either flank of the church, or around the curve of the chevet, a row of heavy and solidly built stone piers with much their greatest horizontal dimension in a direction across the axis of the church; that is to say, each one of them is perhaps twenty feet in and out by three feet or three and a half or four feet in width, measured east and west. Each one of these piers is built in with the low wall outside the outer aisle, or of the chapel, as seen in [Plate XXIX], and the lower part of this wall helps to resist the thrust of the roof-vaulting of that same aisle or chapel. As the pier goes up, it is soon left clear of all walls and roofs, and the flying buttresses from the vaults butt against it.
The Gothic builders had other thoughts over and above their logical desire to show everywhere the true structure. They had also the taste for upward-pointing lines: a taste which seems to have grown with the development of the style. It was not this taste which in the first place made their buildings high as compared with their width: that was a mere matter of convenience and of obtaining very large windows above the aisle roofs. But the pointed arch itself, and the steep roof needed to protect the stone vaults from rain in a rainy climate, led these builders constantly towards the steeper pitch, the sharper point, the more lofty and soaring design.