THIS IS EASY

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Across
  1. 2. Weight hung from a fixed point
  2. 3. Line at which earth and sky appear to meet
  3. 4. Sudden fall of snow down a mountain
  4. 8. Complicated irregular network of passages
  5. 10. Substance used to stimulate immunity
  6. 11. Speak very softly
  7. 12. A gentle, mild breeze
Down
  1. 1. Elaborate musical composition for full orchestra
  2. 2. Self-contradictory statement
  3. 5. Speed of something in a given direction
  4. 6. Obscuring of light from a celestial body
  5. 7. Collection of traditional stories
  6. 9. System of millions or billions of stars