Constitution of the State of Texas 1876 Art. 4, § 17. President pro tempore of Senate serving as Governor;  compensation of Lieutenant Governor and President pro tempore of Senate

(a) If, while exercising the powers and authority appertaining to the office of Governor under Section 16(c) of this article, the Lieutenant Governor becomes temporarily unable or disqualified to serve, is impeached, or is absent from the State, the President pro tempore of the Senate, for the time being, shall exercise the powers and authority appertaining to the office of Governor until the Governor or Lieutenant Governor reassumes those powers and duties.

(b) The Lieutenant Governor shall, while acting as President of the Senate, receive for his or her services the same compensation and mileage which shall be allowed to the members of the Senate, and no more unless the Texas Ethics Commission recommends and the voters approve a higher salary, in which case the salary is that amount;  and during the time the Lieutenant Governor exercises the powers and authority appertaining to the office of Governor, the Lieutenant Governor shall receive in like manner the same compensation which the Governor would have received had the Governor been employed in the duties of that office, and no more.  An increase in the emoluments of the office of Lieutenant Governor does not make a member of the Legislature ineligible to serve in the office of Lieutenant Governor.

(c) The President pro tempore of the Senate shall, during the time that officer exercises the powers and authority appertaining to the office of Governor, receive in like manner the same compensation which the Governor would have received had the Governor been employed in the duties of that office.