.All sums received by a manager on account of any estate in excess of what may be required for the current expenses of the mentally ill person or for the management of his property, shall be paid into the public treasury on account of the estate, and shall be invested from time to time in any of the securities specified in section 20 of the Indian Trusts Act, 1882 (2 of 1882), unless the authority which appointed him, for reasons to be recorded in writing, directs that, in the interests of the mentally ill person such sums be otherwise invested or applied.