The tendency to restrict the exercise of private property rights had been assailed by the theories of _Laissez faire_ and the teachings of Adam Smith, and, as a consequence, all the restrictive mandates of the older forest ordinances had been weakened and had more of less fallen into disuse. Especially the attempts to influence prices and markets had nearly if not entirely vanished during the first decade. Only for the state forest, it was still thought desirable to predetermine wood prices, or at least keep rates low, because wood was a necessary material for the industries. This theory prevailed until, perhaps under the lead of Hundeshagen (see above), the propriety of securing the highest soil rent was recognized as the proper aim, when the practice of selling wood at auction in order to secure the best prices became the rule. The regulations regarding export and import between the different States, which had been enacted under the mercantilistic teachings of the last century (see page 52), and the many tariffs which impeded a free exchange of commodities, lasted for a long while into the 19th century, and were not all abolished until 1865, when under the lead of Prussia, the North German Federation instituted the _Zollverein_ (Tariff alliance) which abolished not only all tariffs between the States of the Federation, but also tariffs on wood products against the outside world. Import duties were, however, again established in 1879, and the policy of protecting the established organized forest management against competition by importations from exploiting countries has been again and again recognized as proper in the revision of tariff rates and railroad freight rates on the government railroads. During the first decades of the century, the supply question was uppermost, and although such men as Pfeil (1816) laughed at the idea of a wood famine, there was good reason, prior to the development of railroads, of coal fields, of iron and steel manufactures, etc., for discussing with apprehension the area and condition of supply and the extent of the consumption. Nevertheless, the attitude of the state toward private property was much more influenced by the economic theories then prevalent, which taught the ideas of private liberty to which the French Revolution had given such forcible expression.