Act of Union continued in sequence from post (1)...(2)...:
"...It is ordained and enacted...that the Lord Chancellor of England or the Lord Keeper of the Great Seal for the time being from time to time and at all times shall have full power and authority by his discretion to nominate and appoint Justices of Peace, Justices of the Quorum and Justices of Gaol in the said counties...by commission under the King's Great Seal;..."
The "Lord Chancellor" or "the Lord Keeper of the Great Seal" were to have full power and authority to nominate and appoint judges in the various courts.
For those interested, a discussion of the judicial system in England can be found:
"The Machinery of Justice in England", by R.M. Jackson, Cambridge, At The University Press, 1940. Chapter I is a historical introduction to the courts and common law.