why wont my battery charge from my alternator on my escort?

my car will start when i use jump leads,it runs for about 10 mins then dies,i have tryd replacing the alternator,but it does the same thing,now iam not sure whether it is the alternator,i have also put another battery in aswell with the same results,maybe its a wiring fault?need diagrams or any help possible.the car is a K Reg 1993 Ford escort.thanks...