Section 9. For the performance of the department’s duties relative to water, gas and electric companies the commission may expend annually for necessary statistics, books, stationery and contingent expenses, and for clerical and other assistance, such sums as the general court shall annually appropriate, and may appoint or employ, subject to the approval of the governor and council, such expert assistance as it may deem advisable, on such terms of office or employment as it may deem proper, and may expend therefor and for the performance of the duties imposed upon it by law such sums as the general court shall annually appropriate.