Ragnarok: the age of fire and gravel
Ignatius Donnelly's 1883 catastrophist treatise, issued by D. Appleton in New York for a general reading public, argues that a comet's debris laid down the glacial drift. The wood-engraved figures are geological plan maps with dense hatched striae, stippled cross-sections of gravel hills studded with boulders, and a shaded rubbing of a scored stone, useful as line-texture fills, contour outlines, and directional hatching.
