Answer:
I know a word of letters three, add two and less there will be.
Makes arrows fly and kites soar!
Big as a saucepan, deep as a cup, Even a river can't fill it up. What is it
It is in every mountain, it's not in any hill, it's not in all the world, and yet it's in the mill.
I start in little but I end in full, you'll find me in half and complete.
It flows out of the soil, It burns you if it boils, And holds us in its coils, More valuable than gold, As black as it is old.