Fresh Blueberry Pie

1    (9 inch) unbaked pie shell
1/3  c. flour
1/2  c. sugar
1/2  tsp. ground cinnamon
4-1/2 c. fresh blueberries
1    Tbsp. lemon juice
1/2  c. firmly packed brown sugar
1    c. flour
1/2  c. margarine or butter

Combine flour, 1/2 c. sugar, cinnamon and 
blueberries.  Mix well and put into pie shell. 
Drizzle top with lemon juice.  Combine 1/2 cup 
brown sugar and flour.  Cut in butter until 
mixture resembles coarse meal.  Spread topping 
over berries.  Bake for 30 minutes at 425 
degrees, then cover with foil and continue 
baking for 20 minutes more.