In the course of seven years such substantial progress had been made that I decided to push into the history of the Age of Reptiles also, and, following the pioneers, Marsh and Cope, to begin exploration in the period which at once marks the dawn of mammalian life and the climax of the evolution of the great amphibious dinosaurs.
In the spring of 1897 we accordingly began exploration in the heart of the Laramie Plains, on the Como Bluffs.

On arrival, we found numbers of massive bones strewn along the base of these bluffs, tumbled from their stratum above, too weather-worn to attract collectors, and serving only to remind one of the time when these animals--the greatest, by far, that nature has ever produced on land--were monarchs of the world.
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.