What is the meaning of "practice scales" and "gauge the names of the books on inkpot"

[chebu]

Could you please teach me the meanings of following boldface words.
They are from a book "Thinking Places" on page138.
Whole sentences can be found on this site.
http://books.google.co.jp/books?id=tLvj--6fCM0C&pg=PA138&lpg=PA138&dq=%22gauge+the+names+of %22&source=bl&ots=fgpyYlltmE&sig=_sugko27pJ_S940-cSDVITgCWj0&hl=ja&ei=S24PTMKMO9CHkQXZ84X7Cw&sa=X&o i=book_result&ct=result&resnum=3&ved=0CB4Q6AEwAg#v =onepage&q=%22gauge%20the%20names%20of%22&f=false

Question 1
"A pair of world globes rest on the floor, one on each side of the table, and nearby a large, Argerian waste-paper basket, much used by Kipling.
As he wrote,"mercifully, the mere act of writing was, and always has been, a physical act, no problem to me. This made it easier to throw away anything that did not turn out well, and to practice, as it were, scales."

What's "This" means in this sentence?
and "to practice scales" is used as a metapher?

Question 2
He had on his desk "an outsize, office pewter inkpot on which I would gauge the names of the books and talks I wrote out of it."

What is "gause the names of the books and talks on inkpot"?


I would be grateful for your help.

[chebu]

To Gillnetter

Thank you very much for your detailed advices!