Some observations on the assiento trade, as it hath been exercised by the South-Sea Company [electronic resource] : proving the damage, which will accrue thereby to the British commerce and plantations in America, and particularly to Jamaica : to which is annexed, a sketch of the advantages of that island to Great Britain, by its annual produce, and by its situation for trade or war : addressed to His Grace the Duke of Newcastle, one of His Majesty's principal secretaries of state / by a person who resided several years at Jamaica.