1851 Great Exhibition: Official Catalogue: Class VIII.: John Pilkington
176. PILKINGTON, JOHN, Goole, Leeds — Inventor.
A wrought-iron keelson, for wood-built ships. Its object is to give a greater degree of strength and durability, without any additional dead-weight, and to obviate the great difficulty in obtaining suitable lengths and sizes of oak timber. This keelson, being tubular and perfectly water-tight, assists in ballasting vessels when clear of cargo, by opening a valve to admit water; it is afterwards let off into the bottom of the ship, and pumped out in the ordinary way. The keelson may be used as a water-tank.
[By lowering the centre of gravity of a ship its stability is increased: the best position for the ballast, therefore, is the lowest, viz., the keelson.—S. C.]