_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. Footnote 25: The following are the _internal areas_ of the three largest churches in Britain:— St. Nicholas’, Great Yarmouth 25,023 sq. ft. St. Michael’s, Coventry 24,015 " Holy Trinity, Hull 21,756 " * * * * * 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] Footnote 26: The brickwork of the chancel and transepts of Holy Trinity, Hull, is probably the ‘earliest existing example of mediæval brickwork in England.’ These portions of the church were built during the first quarter of the fourteenth century. 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.