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. What am I?
I have thirteen hearts but no body or soul.
At night I come without being fetched, and by day I am lost without being stolen. What am I?
I am like thunder in your cranium
The sun bakes me, the hand breaks me, the foot treads on me, and the mouth tastes me. What am I?
What is lighter than what it is made of?