But such small churches are not common. Generally the nave has along each side what is called an aisle, in which case its central roof is supported on a double row of pillars. Possibly the chancel also has aisles. The walls above the lines of pillars may be pierced with windows, which thus look out above the roofs of the aisles. These windows are known as clerestory windows.
| Photo by] | [C. W. Mason |
| A Piscina in Patrington Church | |
In cathedrals and very large churches there is a story which runs along each side of the nave and chancel, between the capitals of the pillars and the clerestory. This is called the triforium. Beverley Minster has a triforium, but there is no passage round it, and it is really a blind story. A portion of it can be seen in the photograph of the Percy Tomb on page [230]. Bridlington Priory Church has a triforium on the north side only.
In churches of large size the building is not simply a rectangular one with or without aisles, but is formed of two rectangular buildings crossing each other at right angles. The nave and chancel have added to them a north transept and a south transept, and above the crossing-place rises a central tower on four huge piers.
These transepts, as well as the nave and chancel, may have aisles. But this is customary only in cathedrals. Holy Trinity Church, Hull, the third largest church in Britain,[[25]] has aisles only to the nave and chancel; Patrington Church—the ‘Queen of Holderness’—has aisles to the nave and to each transept; and Hedon Church—the ‘King of Holderness’—now has aisles only to its nave, though its transepts formerly had an aisle on the east.
Many were the difficulties that the builders of our ancient churches had to overcome. In the East Riding one difficulty was the obtaining of suitable building-material. Stone blocks were costly, for these had to be brought by water from the quarries of the West Riding. So usually the builders had to make the best use they could of the materials they obtained locally—boulders from the cliffs of the sea-shore, blocks of chalk from the Wolds, or clay bricks from the low-lying bank of the Humber.[[26]]
Another difficulty was sometimes encountered in obtaining suitable foundations. The clay soil on which the church of Holy Trinity, Hull, is built was not of sufficient depth to afford foundations for the heavy central tower which it was intended to build.
Twentieth-century builders would drive piles down into the clay to make a firm foundation; the fourteenth-century builders solved the problem by constructing four huge rafts of trimmed oak trunks, each consisting of two rows of trunks crossing at right angles. On these rafts they raised the piers for their tower; and when, in 1906, it became necessary to take out the tree-trunks and replace them with steel girders and cement, many of the trunks were found to be as sound as on the day that they were placed in position six hundred years ago.