As we sailed along we had a great deal of conversation about lifeboats. They have been in existence since 1789, when the first boat built expressly for saving life was launched by Mr H. Greathead, a boat-builder at South Shields; but some years before that a London coach-builder--Mr Lionel Lukin--designed a boat which he called "an unimmergible boat;" and, for the purpose of carrying out his experiments, he purchased a Norway yawl, which he tried in the Thames. His plans were entirely successful.  He soon afterwards fitted a coble, sent from Bamborough, in Northumberland.  The Duke of Northumberland, approving of Mr Greathead's invention, ordered him to build a boat, which was afterwards stationed at North Shields.  For a long time his plan was considered the best, and there are several of his lifeboats, which are impelled exclusively by oars, still in existence.