Any portion of a railroad which has not been completed and opened for use for a period of 10 years next prior to September 15 next preceding the time when a railroad tax is to be assessed shall be exempt from taxation.
RSA 82:25
1868, 18:1. GL 62:1. 1881, 75:1. PS 64:2. PL 69 :27. RL 83:27.