What was found
PHL FLT 80 ENROUTE SAN - PHL, ABOUT AN HOUR AWAY FROM PHL, THE FIRST OFFICER'S WINDSHIELD BEGAN TO ARC, THEN CRACK. QRH PROCEDURES WERE FOLLOWED. FLIGHT LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE REPLACED THE FIRST OFFICER'S WINDSHIELD. OPERATIONALLY CHECKS OK.