The survey of the route of any branch shall not be filed in the office of the secretary of state until the company shall have deposited with the state treasurer at least two thousand dollars for every mile and a proportionate sum for any distance less than a mile of the branch.
The state treasurer shall hold such fund subject to be repaid to the company in installments of two thousand dollars for each mile and a proportionate sum for any distance less than a mile of the branch, upon the construction of which it shall be proved to his satisfaction, that such amount has been expended.
N.J.S. § 48:12-25