Answer:
I go up, let out a load and then go back down. What am I?
Of these things - I have two. One for me - and one for you. And when you ask about the price I simply smile and nod twice.
Lighter than what I am made of. More of me is hidden than seen. What am I?
I have an eye but cannot see. I take time to generate and can dissipate in seconds. What am I?
I carry you down a gentle stream.
What scientists might call your pooch.