Any railroad company described in § 65-8-101 shall have the power to borrow money and to issue its bonds therefor, or for any other indebtedness or liability which it may incur, or may have incurred, in the exercise of its lawful purposes, and to secure the payment of such bonds, with the interest thereon, by a mortgage of the whole or any part of its railroad and equipment and other property and franchises, containing such provisions as its directors shall approve.