theorem Th15:
  (for x st x in X holds x is Ordinal & x c= X) implies
   X is epsilon-transitive epsilon-connected
proof
  assume
A1: for x st x in X holds x is Ordinal & x c= X;
  thus X is epsilon-transitive
  by A1;
  let x,y;
  assume x in X & y in X;
  then x is Ordinal & y is Ordinal by A1;
  hence thesis by Th10;
end;
