Mary takes a few steps down the hill, then starts more urgently heading over to the woman.

El shakes herself, then goes after Mary, catching up quickly and taking the lead.

The woman glances up at them as they approach. "Hello," she says, quietly, walking briskly to the next threatened part of the river.

El trots to keep up.

"How are you doing this?"

"Alchemy."

She shores up another worn-down bank, still with the same clapping and kneeling motion.

"To answer your next question: I have a deeper understanding of what is involved than most. My body forms the circle, and my mind the array."

"Can you teach us how to do it?"

She keeps moving.

"Not trivially, and I do not take students lightly."

El follows.

"We're good at learning."

Mary keeps up, running a few times when she starts to fall behind.

"Really good! We've been teaching ourselves alchemy out of books. We'll be the best students you've ever heard of."

"That won't be easy. Do you think you two can impress me?"

"Yes!"

She indicates an almost collapsed section of dike before them.

"Fix that, then."

Mary starts pulling chalk out of her pockets, then frowns at how wet the ground is.

"It won't hold chalk like this..."

She glances at her sister.

"Unless we dry it first? Then use the umbrella."

"Here, you hold this-" El passes the umbrella to Mary and wipes her hands on her shirt, then gets some chalk of her own and begins sketching an array to dry out the ground on her left hand.

Mary holds the umbrella to block the rain from where El's working.

The woman observes, gaze keen.

"Show me the array you're using. Explain what it does."

El starts explaining as she goes. Defining what she intends to work on, they already know what the ground is made of here so that's fine; the area, just big enough to hold another circle; minimum and maximum rates of energy transfer she's allowing, she catches an error in her math as she talks through this part and fixes it.

The woman nods along.

"You have a good grasp of what you're doing. I want to see you and your sister work together on fixing the dike."

El nods. Once she's finished her array and used it to dry out a patch, she takes the umbrella back from Mary.

Mary talks faster than El, skips around more - but she also has an intuitive grasp of shape and movement, and makes fairly large mental leaps as she talks the dike repair over with her sister. She takes over sketching this, though still consults El on math and symbol position and bounces ideas on how to get the dike properly sturdy off of her.

El has a solid grasp of the foundational and structural principles, and backfills Mary's logic like she's being doing it for years. Which she has.

And together they can get the dike fixed.

The woman examines it, pronouncing their work stable enough to hold, then starts listing and explaining flaws in what they'd been doing.

Wouldn't be much a teacher if she didn't know more than them. El listens carefully.

Mary's capable of focusing when she wants; right now, her attention is centered on the woman's words.