All 3 Uses

solemn
in
I Heard the Owl Call My Name
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When Constable Pearson emerged from the bush, all the eyes were sad again, and all the faces solemn.†
Chpt 1.2 *

solemn = very serious--possibly dignified
They were the great rituals of my people, solemn and important.†
Chpt 2.9
"Calamity wouldn't be separated from them in life," he said gently, "and I don't think he'd want to change now," and for an instant a bit of laughter rose in the solemn eyes beneath the knit caps in all the toughened faces, and was instantly squelched.†
Chpt 4.18

Definitions:

(1) (solemn)
in a very serious (and often dignified) manner
(2) (meaning too rare to warrant focus)
Less commonly, solemn can mean that something was done with great or appropriate ceremony. It can also be used to describe something as dark or undecorated.