The University may provide by statute that members of the Senate may vote at any election of a Chancellor or High Steward of the University by proxy, such proxy being a member of the Senate authorized by an instrument in writing signed by the member nominating such proxy; but no member shall be entitled to vote as a proxy unless the instrument appointing him has been transmitted to the Vice-Chancellor not less than forty-eight hours before the time appointed for holding such election of a Chancellor or High Steward, as the case may be; and such instrument may be in the form contained in the schedule to this Act annexed.