What are the words of the poem, "Too solemn by day" by William Sidney
Walker(1795-1846)? Or where could I find them?

Here are the words to William Sidney Walker's "Too Solemn for Day, Too
Sweet for Night":

"TOO solemn for day, too sweet for night, 
   Come not in darkness, come not in light; 
 But come in some twilight interim, 
   When the gloom is soft, and the light is dim."

Here are three websites which reproduce the poem:

PoemHunter
http://www.poemhunter.com/p/m/poem.asp?poem=38174&poet=7194&num=1&total=1

Bartleby
http://www.bartleby.com/101/639.html

Project Gutenberg Book of English Verse 
http://john.fremlin.de/pgbev/poems/pgbev-639.html

Google search strategy:

Google Web Search: "william sidney walker" + "too solemn for day"
://www.google.com/search?hl=en&ie=UTF-8&oe=UTF-8&q=%22william+sidney+walker%22+%22too+solemn+for+day

I hope this is helpful. If anything is unclear, or if a link does not
function, please request clarification. I'll be glad to offer further
assistance before you rate my answer.

Best wishes,
pinkfreud

Answered exactly the question(s) asked. Nothing in excess.