Here the author explains how the sailors' songs act as a disguise, enabling the sailors to reveal their opinions to the captain 'without expressing them to his face.' We are also given an impression of the horrendous food given to the crew during long voyages. Sailors referred to pork as 'measles', and to salt beef as 'horse'.
About Sailors' Language
This collection of sea-terms is a fascinating lexicon of odd words and phrases. Most of words listed in the book would be incomprehensible to 'landlubbers' - as the author states in the preface, ' sailors' talk is a dialect as distinct from ordinary English as Hindustanee is, or Chinese.' As well as technical terms referring to various parts of the ship, the book is full of language that reveals the hardships of life at sea.