Good Riddles

Question: Before your choose the witching hour, take care to dream the tallest tower. Than careful before you leave too soon--behold the dark and hollow moon. What's the number? (This Riddle is from the Eye of Minds, by James Dashner.)

Question: Until I am measured, I am not known. Yet how you miss me, When I have flown What am I?

Question: Disgusting and small, we wriggle through your halls, devouring books, cloths and walls. Alone we are feeble, together we have some might, glinting in our damp holes at night. What are we?

Question: A farmer has 10 cows, all but six die. How many are left?

Question: I can be shared by many or spread to few, I am as fragile as silk yet as strong as steel. Wars have been fought in my name, generations defined by me. What am I?