By 18 June two piers and four pier heads were working. The north pier features a more minimalist design compared to the other two piers. Such long bridges required support from either piers or pontoons. Barry designed a bridge with two bridge towers built on piers. There are also four smaller non-navigable channels between nine concrete piers and two abutments. The central dome rises on four arches standing on colossal piers. This was a girder bridge on stone piers. Cruise ships now dock at all three piers. The bridge had eight piers and seven spans. Other instruments are often mounted in insulated enclosures on small buried piers of unreinforced concrete. Pontcysyllte Aqueduct is an iron trough on tall stone piers. An arcade is a row of arches, supported on piers or columns. The bridge rests on 62 piers, of which the 44 main piers are apart. "Beetles" were pontoons that supported the "Whale" piers. This is opposed to viaducts using continuous spans over the piers.