If any railway corporation, within two years after its articles of association have been filed and recorded, does not begin the construction of its road and expend thereon twenty percent of the amount of its capital within five years after the date of its organization, its corporate existence and power shall cease; but any such railway corporation at any time may reduce its capital stock in the manner and form provided by the laws of this state, and if twenty percent of the amount of its capital, as so reduced, has at any time been expended in good faith in the construction of its road, then its corporate existence and power shall not cease or be deemed to have ceased.