Across the Great Barrier by Patricia C. Wrede
Eff is asked to travel past the Barrier Spell and into the unprotected territory of the far west. She finally convinces her mother to let her go. At first, it seems to be no dangerous trip, since they have magic to protect them. But then they see weird things. Wild cats hanging out in unusual places in unusual groups and plants growing in strange places. These may be just a result of teh mirror bugs from the season before, but a frightening and stange discovery tells them otherwise.
When they stop to camp for the night, Eff and Professor Torgeson find stone statues of animals that are perfectly carved-a little to perfect. Is some unknown creature turning thae animals to stone? Will it be a threat to the settlers, or is it something from a long time ago?
*Book 2 in 'Frontier Magic'*
Previous book: Thirteenth Child