BLACKFORD COUNTY, INDIANA, 1926
As the green truck rattles over rutted roads,
Marie Tharp sways and bumps beside her father.
They hike through fields, where he digs up dirt
he labels. One patch of soil may predict how tall
a field of corn may grow. Papa also tests for signs
of oil or water. Vast lakes lie under the hard ground,
he says. Rock and water keep changing place.
He puts down his shovel, then sets up a tripod.
He measures angles between where they stand,
the horizon, and a point overhead called the zenith.
Much must be known to make a map,
which he does for the US Department of Agriculture.
Papa explains how math saves time.
Instead of spending days hiking from one place
to another, counting steps,
he takes measurements and multiplies.
I’m not the first to note cliffs or curves in rivers,
Papa says as he picks up and pockets an arrowhead.
People who lived here before anyone had paper
found ways to make good maps.
Marie tests which tree trunks best fit in her arms.
They form circles like the middle of a globe,
but instead of curving in at the top and bottom,
the branches and roots spread out.
Her rubber boots leave footprints in mud
as she searches for abandoned bird nests,
snake skins, fossils, and feathers.
Earth is like a book the wise can read.
Marie turns over a rock, sees a spider scuttle.