Definition of "phænomenon"

It is eaſy to obſerve how many empty hypotheſis and idle reaſonings the phænomenons of this river have put mankind to the expence of.

1735, Jerome Lobo, translated by Samuel Johnson, A Voyage to Abyssinia, […], London: […] Elliot and Kay, […], and C. Elliot, Edinburgh, published 1789, page 116

This wonderful phænomenon has, ſince it was firſt diſcovered, employed the thoughts of very able philoſophers ; many hypotheſes having been offered, not only for its explanation, but even to foretel the future variations in various parts of the world.

November 16, 1786, Tiberius Cavallo, Magnetical Experiments and Obſervations, page #22