Dissolve gelatin in boiling water. Add cold water. Spread 1 cup fruit cocktail in bottom of 12-cup fluted pan. Pour in 1.5 cups gelatin mixture. Brush crumbs off cake and place topside down, over fruit and gelatin, pressing down lightly. Spoon remaining fruit cocktail around side of cake. Pour remaining gelatin over cake. Chill until firm, four hours. Unmold and serve.