Answer:
Hard to catch, easy to hold. Can't be seen, unless it's cold.
I scribble forms of the finest letter, And repel elements of the harshest weather. I am an arrow-aimer and a dust-breaker.
I am black when I am clean and white when I am dirty?
This only turns over once you have travelled very far. What is it?
My life can be measured in hours, I serve by being devoured. Thin, I am quick. Fat, I am slow. Wind is my foe.
I’m grown from darkness but shine with a pale light. Very round I am and always a lady's delight.