The Wealth of Nations by Part 1 Chapter 10 Page 33

In time of peace, and in the merchant service, the London price is from a guinea to about seven-and-twenty shillings the calendar month. A common labourer in London, at the rate of nine or ten shillings a week, may earn in the calendar month from forty to five-and-forty shillings. The sailor, indeed, over and above his pay, is supplied with provisions. Their value, however, may not perhaps always exceed the difference between his pay and that of the common labourer; and though it sometimes should, the excess will not be clear gain to the sailor, because he cannot share it with his wife and family, whom he must maintain out of his wages at home.

The dangers and hairbreadth escapes of a life of adventures, instead of disheartening young people, seem frequently to recommend a trade to them.