Which preposition to use with appulses

of Occurrences 3%

The first of these is, the introduction of the American method of observing transits, by completing a galvanic circuit by means of a touch of the finger at the instant of appulse of the transiting body to the wire of the instrument, which circuit will then animate a magnet that will make an impression upon a moving paper.

Which preposition to use with  appulses