1. animal that nurses its young in a pouch.   Hint First letter clue   2. residue from smelting operation.   First letter clue   3. band of colors formed when light passes though a prism.   First letter clue   4. stitching of parts at their edges; thread or wire.   First letter clue   5. path followed by body under forces.   First letter clue   6. natural environment; nutrient setting for microorganism.   First letter clue   7. optical illusion due to atmospheric conditions.   First letter clue