The first thing that waked her to fuller consciousness was the cessation of the rain, and a perception that the darkness was divided by the faintest light, which parted the overhanging gloom from the immeasurable watery level below.
There are no more uses of "immeasurable" in the book.
Show samples from other sources
"While I’m sure we’re all immeasurably relieved that you’ll be looking after the Blackthorn children," said Luke, "Helen is one of them.
Cassandra Clare -- City of Heavenly Fire
I settled into rituals, which improved the quality of my existence immeasurably.