On the determination of the orbits of comets : According to the methods of Father Boscovich and Mr. De La Place. With new and complete tables; and examples of the calculation by both methods. By Sir Henry Englefield, bart. F.R.S. & F.A.S. - Englefield, Henry, (Printed by Ritchie and Sammells, for Peter Elmsly, in the Strand,, 1793)