The specific number of justices who sit on the united states supreme court is determined by

The specific number of justices who sit on the United States Supreme Court is determined by Congress. The U.S. Supreme Court possesses jurisdiction over all federal courts as well as state courts which handle issues concerning federal laws. The justices, once they have been appointed, have lifetime tenure unless they get impeached, choose to resign, or decide to retire.  

The colony was represented by the house of burgesses