Art. 20. The position of Director shall be held by a person who is a specialist in any one of the technical sections, and at the same time shall be its chief, an indispensable condition being that in addition to his technical knowledge he shall have had a practical apprenticeship. Art. 21. The technical positions may be filled, by contract, by native or foreign professors of established ability. Art. 22. To each of the stations there shall be sent a special regulation determining for them their proportions according to the necessities of the case, fixing the term and salaries of their respective personnel and providing for the special necessities to come. TITLE II The creation of the Refining and Manufacturing Rubber Industries ONLY CHAPTER Art. 23. The first factory for the refining of seringa rubber that shall be established in each of the cities of Belém (Pará) and Manáos, and of maniçoba and mangabeira rubber which shall be established in the States of Piauhy, Ceará, Rio Grande do Norte, Pernambuco, Bahia, Minas Geraes and S. Paulo, as well as the first factory of rubber articles which shall be established in Manáos, in Belém, in Recife (Pernambuco) in Bahia, and in Rio de Janeiro, there shall be conceded the following premiums and favors: (a) Up to 400,000 milreis in money to the plants for the refining of seringa rubber; Up to 100,000 milreis in money to the plants for the refining of maniçoba and mangabeira rubber; Up to 500,000 milreis in money for plants for manufacturing rubber articles. (b) Exemption from import duties, including fees in the manner and by the processes described in Articles 3 and 91 combined, as the case may require, for all material, machines, utensils and hardware necessary for the construction and complete equipment of the factory, as well as all chemical substances, cloth and different materials, combustibles and lubricants necessary for the working and maintenance of the factory, during a period of 25 years. (c) The right of appropriation for public use, according to the legislation in force, of the lands and improvements belonging to individuals that may be judged appropriate and necessary for the equipment of the factory and its dependencies. (d) A preference given by the Government for the purchase of the products used in the service of the Army and Navy and the federal public departments, which shall be manufactured by the factories, when they can compete in quality with similar foreign articles—the contract for furnishing the same, adjudicated every 3 years with each factory, for those of their products which were classified in the first place in the expositions mentioned in Article 95. (e) Exemption from all State and Municipal duties for the same time as in letter b, because the factory is considered to be of service to the Government.