8. Congress alone has power to lay these duties. There are two modes of imposing them; sometimes one and sometimes the other being adopted, according to the views of the Congress legislating. They are called specific and ad valorem duties. Ad valorem means, according to the cost, and is counted on the cost in the country the article comes from. Specific duties are so much on the article, without regard to the cost. On many things imported there is no duty, and they are called “free goods.” Changes are continually made in the tariff to conform to the requirements of the Treasury, the desires of the people, and the changing views of the legislators. DRAWBACKS. 9. When the duties on foreign goods have been paid, and they are afterwards exported, the duties which have been paid are refunded to the owner. The money thus paid back is called a drawback. All imported goods are entitled to drawback whenever they are taken out of the United States. BOUNTIES ON EXPORTED GOODS, take money out of, instead of putting it in the treasury, yet the government in a few cases has allowed bounties upon exported articles. Fish taken by American vessels, refined sugar and distilled spirits made from imported sugar and molasses, are examples. This was done to encourage domestic industry and enterprise. CUSTOMS REVENUE FOR FIFTY-ONE YEARS. A Comparative Statement showing the Customs Revenue, Amount of Dutiable and Free Goods Imported, and the Average Rate of Duty on Imports, every year from 1821 to 1871, inclusive.