In the Days of the Comet is a science fiction novel in which humanity is "exalted" when a comet causes "the nitrogen of the air, the old azote," to "change out of itself" and become "a respirable gas, differing indeed from oxygen, but helping and sustaining its action, a bath of strength and healing for nerve and brain." The result: "The great Change has come for evermore, happiness and beauty are our atmosphere, there is peace on earth and good will to all men."