Whenever a justice is satisfied that a jury sworn in a cause before him, after having been out a reasonable time, cannot agree on their verdict, he may discharge them and shall immediately issue a new summons for another to appear, at a time therein fixed, not more than three (3) days distant, unless the parties consent that the justice may render judgment upon the evidence already before him, which he may do in that case, or unless they consent that the new trial, upon a new hearing of the evidence to be adduced by the parties, shall be by the justice.