Sentence:  In order to prevent any accidents which might happen, by the iron pin of the carriage giving way, from so sudden a shock, a <WSD>breechen</WSD> is made fast, from the sliding carriage, to the head of the boat, and properly secured: the gun being fired, the elasticity of the <WSD>breechen</WSD> permits her to recoil about two inches, which certainly is a much less strain to the boat, and a safer method of using the gun; for, allowing the <WSD>breechen</WSD> to break, there is then the same principle of the iron pin to be depended upon, as at present. 
Meaning of the word marked with <WSD> tags:  (historical) A rope used to limit the recoil of a cannon on a ship