The department of revenue shall, for the purpose of determining what amount shall be assessed to any one of the companies in each county of the state into which the line or lines of the company extend, multiply the assessed or taxable value per mile of line of the company, as ascertained according to the provisions of this chapter, by the number of miles of line in each of the counties, and the result thereof shall be certified by the department to the several county auditors of the respective counties into, over, or through which the line or lines extend.