Abstract
For pt.IV see ibid., vol.9, p.725 (1976). By introducing a notional field variable lambda into the percolation problem, a function Pc( lambda ) is defined whose Ising analogue is the magnetic field variation of the magnetization along the critical isotherm. Series expansions are used to study the critical behaviour of Pc( lambda ) characterized by an exponent delta p, for both site and bond percolation problems on the more common two-dimensional lattices. The authors conclude that delta p is a dimensional invariant and estimate delta p=18.0+or-0.75. It appears that delta p=18, lambda p=23/7, beta p=1/7 is the simplest set of rational exponents which is most consistent with the available data and which satisfies the scaling law gamma p= beta p( delta p-1) exactly.