Steam clams and pry open. (If anyone needs help in how to do this, ask me). Drain off liquid and measure; there should be about 1 cup. Cut clams finely with kitchen scissors. Cook potatoes (about 2 cups cubed) in water until just tender; do not drain. Cut salt pork into 3/8-inch cubes and render over low heat in a large saucepan. Add onion and celery and saute' 3 minutes. Blend flour evenly into this mixture. Add tomatoes gradually, stirring to keep smooth. Add potatoes and their liquid, clams, clam broth and seasonings. Heat quickly to boiling. Serve at once. Makes about 7 cups, or about 6 servings.