Wikipedia
Longitudinal framing (also called the Isherwood system after British naval architect Sir Joseph Isherwood, who patented it in 1906) is a method of ship construction in which large, widely spaced transverse frames are used in conjunction with light, closely spaced longitudinal members. This method, Isherwood felt, lent a ship much greater longitudinal strength than in ships built in the traditional method, where a series of transverse frames were fit together closely from the keel upwards.
Longitudinal framing was a known method of shipbuilding before Isherwood. Naval engineer J. Scott Russell, for instance, had built several longitudinally framed ships, including the SS Great Eastern. However, no one had made the process practical from a commercial standpoint, which was Isherwood's achievement. The first commercial vessel constructed with the Isherwood system, the oil-tank steamer Paul Paix, of some 6,600 tons deadweight in 1908, was scrutinized by other shipbuilders and owners. The success of it and the first general cargo liner to be constructed on the "Isherwood" system, the Gascony in early 1909, encouraged builders in a number of countries to use longitudinal framing as well.