All to the north the rain had dragged black tendrils down from the thunderclouds like tracings of lampblack fallen in a beaker and in the night they could hear the drum of rain miles away on the prairie. They ascended through a rocky pass and lightening shaped out the distant shivering mountains and lightening rang the stones about and tufts of blue fire clung to the horses like incandescent elementals that would not be driven off.  Soft smelterlights advanced upon the metal of the harness, lights ran blue and liquid on the barrels of the guns.

McCarthy, Cormac. Blood Meridian, Or the Evening Redness in the West. Chapter XIV.