A y,Ȳ diagram analysis has been made of two -surface optical systems. The surfaces are spherical and are rotationally symmetric about the optical axis. When the systems are normalized and one of the conjugate planes is at infinity, unique relationships exist between the radii and separations of the optical systems and the y,Ȳ diagram parameters. The aberration coefficients are obtained in terms of the first-order constraints of the y,Ȳ diagram. The y,Ȳ diagram parameters of two-surface systems having zero third-order spherical aberration are represented by a one -parameter family of solutions. The pupil position may be obtained by eliminating zero third-order astigmatism. When the two two-surface systems are placed back to back, each system having zero third -order spherical aberration, a free parameter defines the relationship between the two systems.

Asgrow RX947 was the leading yellow corn hybrid with a yield of 9255 pounds per acre and a net return (after drying) of $447.93 per acre. It was followed by Cargill 8127 (a new entry) and Pioneer 3162 (the top yielding hybrid from the Bonita area). Cargill 9402W lead the white corn hybrids with a yield of 8464 pounds per acre and a net yield of $484.97 per acre. It was followed by Garst 8101W (last years winner) and Pioneer 3281W It is noted that the income from white corn was higher than yellow corn with lower yields. This is due to an $0.85 per cwt premium used in the calculations.