The beginning of England's oppressive policy towards the commerce of her colonies must date from 1651, when Parliament passed a stringent Navigation Act, forbidding the importation of any commodities into England or its territories except in English vessels or vessels of the nation that produced the goods.[196] This law was aimed chiefly at the Dutch carrying trade, which was so extensive that it had aroused England's jealousy, but it came as a serious blow to Virginia. A large part of her exports had for many years been transported by the Dutch, and the entire exclusion of the "Hollanders" could not fail to react unfavorably upon her prosperity. The immediate effect, since it relieved the English ship owners of much of the competition with which they had contended, was to raise the cost of transportation. The Virginians protested strongly. In a speech to the Assembly, Governor Berkeley, fairly foaming with rage, denounced the act. "We," he said, "the Governor, Councell and Burgesses of Virginia, have seene a printed paper ... wherein (with other plantations of America) we are prohibited trade and commerce with all but such as the present power shall allow of: ... we think we can easily find out the cause of this the excluding us the society of nations, which bring us necessaries for what our country produces: And that is the averice of a few interested persons, who endeavour to rob us of all we sweat and labor for."[197] But the evil was to some extent avoided during the Commonwealth period, owing to constant evasions of the law. There is abundant evidence to show that the Dutch trade, although hampered, was by no means stamped out, and Dutch vessels continued to carry the Virginia tobacco just as they had done during the reign of Charles I. In the year 1657, there was a determined effort to enforce the law, and the advance in the charges of transporting the crop of that year, indicates that this effort was partly successful. The freight rate rose from £4 a ton to £8 or £9, and in some cases to £14.[198] A more serious blow came in 1660. A bill was passed prescribing that no goods of any description should be imported into or exported from any of the king's territories "in Asia, Africa, or America, in any other than English, Irish, or plantation built ships."[199] It was also required that at least three-fourths of the mariners of these ships should be Englishmen. Moreover, another feature was added to the law which was far more oppressive than the first provision. It was enacted that "no sugar, tobacco, cotton, wool, indigo, ginger, justic, and other dying woods, of the growth or manufacture of our Asian, African, or American colonies, shall be shipped from the said colonies to any place but to England, Ireland, or to some other of his Majesty's plantations."