Combine pitted cherries with 2 cups sugar and 2 cups water. Boil gently without stirring for 5 minutes, or until foaming ceases. Remove from heat. Combine remaining 1/2 cup water and 1/2 cup sugar, cornstarch, and salt. Mix until cornstarch is well dispersed. Add to the cooked cherries; stir just enough to distribute starch into cherries. Bring to a gentle boil and hold for 1 minute. Pour while boiling into hot jars to within 1 inch of top. Place lids, and screw on bands firmly. Immediately place into a boiling water bath or steam canner and process for 30 minutes at sea level (add 2 minutes processing time for each 1000 feet above sea level). (Recipe courtesy of Utah State University Extension.)