Combine crumbs, sugar and butter or margarine in a small bowl; blend well. Press firmly over bottom of an 8-inch spring-form pan. Chill. Combine sugar, water and cream of tartar in a small saucepan; bring to boiling. Boil rapidly 8 to 10 minutes or until syrup registers 236 degrees on a candy thermometer (or until syrup spins a 2-inch thread when dropped from a spoon). Meanwhile, in large bowl of electric mixer, beat egg whites until stiff peaks form; pour hot syrup in a thin stream over beaten egg whites while continuing to beat constantly. Continue beating until very stiff peaks form and mixture cools (approximately 15 minutes). Set aside. Using electric mixer, beat together cream cheese and sour cream until light and fluffy; beat in vanilla and lemon rind (1/4 teaspoon of ReaLemon juice can be substituted effec- tively). Add 1/4 of the egg white mixture and stir by hand to combine well. Fold remaining egg white mixture into cream cheese mixture until no streaks remains. Spoon about 1/4 of mixture into prepared spring-form pan; drizzle part of blueber- ry preserves over; continue to layer cheese mixture and pre- serves in this way. Freeze overnight or until firm. Decorate with whipped cream and blueberries. This is a sure-fire compliment-getting summer dessert! If you prefer, strawberry preserves and fresh strawberries may be substituted for blueberries. Recipe by: Ken Gregg Posted to MC-Recipe Digest V1 #374, by Michael Ward on Wed, 15 Jan 1997.