The 21th Imrovement

Consists in forming the lower mast out of four spars pyramidically placed in the vessel -- their bases rest in the hold on cross-steps, which extend several feet across the keelson, and the pyramid tapers gradually to the mast-head, where the four spars meet, and are braced together by the trussel-trees and cap.

By this plan the masts and rigging might be secured without throwing any pressure upon the sides of a ship -- for as every one of the four spars passes through the deck, and is fixed to a step in the lower part of the ship's hold, their is no pressure elsewhere than upon the ship's keelson and floors.

Shipwreck and Collisions at Sea greatly prevented by Christophers' Patent Improvements in Naval Archtecture. With four plates.
London: J. Olliver, 59, Pall Mall; P. Richardson, 23, Cornhill. Liverpool: Deighton & Laughton. M.DCCC.L. 8vo, (4), 112 p, 4 pl.

Transcribed by Lars Bruzelius

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