Mix the salt, flour, sugar, cream of tartar, and baking soda together in a large bowl. Cut in the butter, until the mixture resembles coarse gravel. Mix the sour cream and egg together in a small bowl. Make a well in the flour mixture and pour in the sour cream mixture. Mix until most of the mixture is moistened. Gently fold in the blueberries. Turn the mixture out onto a floured work surface and gently incorporate berries. Take care not to over mix. Make 2 balls of dough, and flatten each into 6 inch circles on a lightly sprayed cookie sheet, about 3 inches apart. Cut each circle into 4 wedges; do no separate. Bake the scones at 375 degrees for 10-15 minutes or until the scones are lightly golden brown. Cut the wedges apart. Serve warm or cool.