Section 75. No railroad corporation shall purchase or take by eminent domain or enter upon or use, except for making surveys, any land or other property for the construction of its railroad or of any branch or extension thereof until the county commissioners of the county where such land or other property is situated, after hearing the parties, have determined the manner in which the railroad shall cross the highways and other ways within such county, nor until it has obtained from the department the consent required by sections ninety-seven and one hundred and two in all cases in which the county commissioners adjudge that public necessity requires the crossing at the same level; and notice of such hearing shall be given by publication for three successive weeks in one or more newspapers published in such county, the last publication to be at least seven days before the hearing.