Cook tomatoes until soft; press through sieve or food mill. Combine onions, celery, peppers and carrots. Add enough water to cover. Cook until soft. Press through sieve or food mill. Add to tomatoes. Add salt. Cook slowly until thick, about 1 hour. Stir to prevent scorching. Pour soup into clean hot jars, leaving 1 inch head space. Adjust lids. Process at 10 pounds pressure: 20 minutes for pints; 30 minutes for quarts.