1. acoustics   triangular tract of mud or sand at river's mouth.   tree bearing fruit-cones.   parallelism or similarity.   science dealing with sound.   Hint Half-n-half Clue   2. chisel   sharp-edged tool used for cutting.   druggist or chemist.   proposition that follows without separate proof.   constituent or element.   Half-n-half Clue   3. flora   plants of a region.   defect in eye or lens preventing proper focusing.   ability of system to maintain stability.   correspondence or harmonious relation.   Half-n-half Clue   4. effervescence   continuous flow or series of changes.   giving off of gas bubbles or exuberance.   mutual relation.   agent to speed up chemical reaction without it changing.   Half-n-half Clue   5. apogee   disproportion or lack of balance.   reduction in size.   point in orbit farthest from earth or climax.   drug that reduces pain.   Half-n-half Clue   6. floe   continuous flow or series of changes.   floating sheet of ice.   confused state of mind.   point on which lever is supported.   Half-n-half Clue   7. emetic   conjecture or logical projection beyond range.   reservoir or tank for water.   tooth of a wheel.   medicine that causes vomiting.   Half-n-half Clue