Adverbial Phrase, Parenthetical Phrase, or Something Different?

Question

“It was a dark and stormy night; the rain fell in torrents, except at occasional intervals, when it was checked by a violent gust of wind which swept up the streets (for it is in London that our scene lies), rattling along the housetops, and fiercely agitating the scanty flame of the lamps that struggled against the darkness.” ― Edward Bulwer-Lytton

In this, I maybe thought except at occasional intervals seemed like maybe an adverbial phrase maybe placing information on how it fell. Maybe it doesn't seem to place information on how it falls, it may place information on how it may not fall. So then I guess I thought maybe it seemed like a parenthetical? May except at occasional intervals seem like an adverbial phrase, parenthetical phrase, or maybe something different?

Answer 1

The except-phrase refers to those times when the rain does not fall in torrents, that is, when gusts of wind "check" the rain. To check means to rebuff, to repulse, to hold off, to oppose. The rain is blown back by the wind.

The athlete climbed up the stairs of the Washington Monument at a very rapid pace, except when he encountered groups of senior citizens or families with young children ahead of him, when he had to wait until they moved aside to let him by.

The except-when phrase in the climbing example above does not modify "climbed" alone, but applies to the idea as a whole: climbed-at-a-very-rapid-pace.

Except...at intervals and except...when refer to some kind of interruption or difference in the action which is specified by the verb-phrase in the main clause.