Aroused from sleep on a clear evening in camp by the heavy rumble of a passing Union Pacific freight-train[21], I shall never forget my meditations on the contrast between the imaginary picture of the great Age of Dinosaurs, fertile in cycads and in a wonderful variety of reptiles, and the present age of steam, of heavy locomotives toiling through the semi-arid and partly desert Laramie Plains. So many animals had already been removed from these bluffs that we were not very sanguine of finding more; but after a fortnight our prospecting was rewarded by finding parts of skeletons of the long-limbed dinosaur _Diplodocus_ and of the heavy-limbed dinosaur _Brontosaurus_. The whole summer was occupied in taking these animals out for shipment to the East, the so-called "plaster method" of removal being applied with the greatest success. Briefly, this is a surgical device applied on a large scale for the "setting" of the much-fractured bones of a fossilized skeleton. It consists in setting great blocks of the skeleton, stone and all, in a firm capsule of plaster subsequently reinforced by great splints of wood, firmly drawn together with wet rawhide. The object is to keep all the fragments and splinters of bone together until it can reach the skilful hands of the museum preparator. _The Rock Waves Connecting the Bluffs and the Quarry._ The Como Bluffs are about ten miles south of the Bone-Cabin Quarry; between them is a broad stretch of the Laramie Plains. The exposed bone layer in the two localities is of the same age, and originally was a continuous level stratum which may be designated as the "dinosaur beds;" but this stratum, disturbed and crowded by the uplifting of the not far-distant Laramie range of mountains and the Freeze Out Hills, was thrown into a number of great folds or rock waves. Large portions, especially of the upfolds, or "anticlines," of the waves, have been subsequently removed by erosion; the edges of these upfolds have been exposed, thus weathering out their fossilized contents, while downfolds are still buried beneath the earth for the explorers of coming centuries.