So great was the business before the Lords of Trade that the colonies had to keep skilled agents in London to protect their interests. As common grievances against the operation of this machinery of control arose, there appeared in each colony a considerable body of men, with the merchants in the lead, who chafed at the restraints imposed on their enterprise. Only a powerful blow was needed to weld these bodies into a common mass nourishing the spirit of colonial nationalism. When to the repeated minor irritations were added general and sweeping measures of Parliament applying to every colony, the rebound came in the Revolution. =Parliamentary Control over Colonial Affairs.=--As soon as Parliament gained in power at the expense of the king, it reached out to bring the American colonies under its sway as well. Between the execution of Charles I and the accession of George III, there was enacted an immense body of legislation regulating the shipping, trade, and manufactures of America. All of it, based on the "mercantile" theory then prevalent in all countries of Europe, was designed to control the overseas plantations in such a way as to foster the commercial and business interests of the mother country, where merchants and men of finance had got the upper hand. According to this theory, the colonies of the British empire should be confined to agriculture and the production of raw materials, and forced to buy their manufactured goods of England. _The Navigation Acts._--In the first rank among these measures of British colonial policy must be placed the navigation laws framed for the purpose of building up the British merchant marine and navy--arms so essential in defending the colonies against the Spanish, Dutch, and French. The beginning of this type of legislation was made in 1651 and it was worked out into a system early in the reign of Charles II (1660-85). The Navigation Acts, in effect, gave a monopoly of colonial commerce to British ships. No trade could be carried on between Great Britain and her dominions save in vessels built and manned by British subjects. No European goods could be brought to America save in the ships of the country that produced them or in English ships. These laws, which were almost fatal to Dutch shipping in America, fell with severity upon the colonists, compelling them to pay higher freight rates. The adverse effect, however, was short-lived, for the measures stimulated shipbuilding in the colonies, where the abundance of raw materials gave the master builders of America an advantage over those of the mother country. Thus the colonists in the end profited from the restrictive policy written into the Navigation Acts.