§11. To be eligible to the office of president or vice-president, a person must be a natural born citizen of the United States, thirty-five years of age, and must have been fourteen years a resident within the United States. The reasons for requiring long terms of citizenship and residence, and mature age and experience, in the case of senators, apply with equal force in the case of president. §12. In case of a vacancy in the office of president, the vice-president becomes the president. The power of making further provision for supplying vacancies is, by the constitution, given to congress. (Art. 2, §1.) Congress has accordingly enacted, that, when there is neither president nor vice-president, the president _pro tempore_ shall act as president; and if there should be none, the speaker of the house of representatives would assume the duties of the office. §13. The same section declares that the salary of the president shall neither be increased nor diminished during the time for which he shall have been elected. It would be improper to allow congress to reduce his salary at pleasure. This would make the executive dependent upon the legislature for his support. On the other hand, if his compensation could be increased during his official term, he might be tempted to use undue influence to procure a needless increase of his salary. §14. The presidential term commences the 4th of March next after the election, and ends the 3d day of March four years thereafter. Each successive congress also commences and ends its term every two years, on the same days of that month; and it is called a new congress, although only one-third of the senators go out of office when a congress is said to expire, and are succeeded by new ones when the next congress is said to commence its official term. Chapter XL. Powers and Duties of the President; Treaties; Public Ministers; Appointments and Removals. §1. The powers and duties of the president are next given. "The president shall be commander-in-chief of the army and navy of the United States, and of the militia of the several states when called into the actual service of the United States." (Art. 2, §2.) Some of the reasons for giving to the executive the command of the public forces, have been given. (Chap. XXV, §2, 5.) It has also been observed, that a prompt and effectual execution of the laws is best secured by intrusting this power to a single individual. (Chap. XXXVIII, §2.) The constitution, (Art. I, §8, clauses 12-16,) give congress power over the army, navy, and militia, and "to provide for calling forth the militia to execute the laws of the union, suppress insurrections, and repel invasions." As this power is to be exercised upon sudden emergencies, congress has by law authorized the president to call out the militia for these purposes. And as the direction of the public forces is a power of an executive nature, it is intrusted to the executive.