Line a 9-inch pie plate with pastry.
Pour blueberries into pie.
Add 1/4 cup of the raspberries.
In a saucepan, cook remaining 1 cup raspberries in water for 5 minutes.
In a small bowl, combine sugar and cornstarch.
Add to saucepan and cook, stirring constantly, for about 4 or 5 minutes, or until glaze thickens.
Pour glaze over pie.
Refrigerate for 3 or 4 hours; serve cold.