A light exists in spring
Not present on
Dickinson's grammar twist—'on the year' instead of 'in the year.' She makes time a surface the light sits on, not a container it fills.
science cannot overtake
**Overtake** means to catch up with something moving. The light is fleeing and science is chasing—but losing the race.
horizons step
Horizons don't move—we do. She's reversed subject and object, making the landscape active and herself passive.
formula of sound
**Formula** = scientific language again. The light leaves without equations, without measurement, without any system to capture it.
trade had suddenly encroached
**Trade** = commerce, buying and selling. **Sacrament** = holy ritual. She's comparing the loss of spring light to capitalism invading a church.