Answer:
Brown I am and much admired; many horses have I tried; tire a horse and worry a man; tell me this riddle if you can.
I am a shower that lights up the sky
What goes all around the world but never leaves its corner?
Though I am only two words I have thousands of letters in me
What gets broken without being held?
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.