He had resolved, nevertheless, to do some local boring as part of the expedition’s general program; hence he set up the drill and put five men to work with it while the rest finished settling the camp and repairing the damaged aeroplane. The softest visible rock – a sandstone about a quarter of a mile from the camp – had been chosen for the first sampling; and the drill made excellent progress without much supplementary blasting. It was about three hours afterward, following the first really heavy blast of the operation, that the shouting of the drill crew was heard; and that young Gedney – the acting foreman – rushed into the camp with the startling news.

They had struck a cave. Early in the boring the sandstone had given place to a vein of Comanchian limestone, full of minute fossil cephalopods, corals, echini, and spirifera, and with occasional suggestions of siliceous sponges and marine vertebrate bones – the latter probably of teleosts, sharks, and ganoids. This, in itself, was important enough, as affording the first vertebrate fossils the expedition had yet secured; but when shortly afterward the drill head dropped through the stratum into apparent vacancy, a wholly new and doubly intense wave of excitement spread among the excavators. A good-sized blast had laid open the subterrene secret; and now, through a jagged aperture perhaps five feet across and three feet thick, there yawned before the avid searchers a section of shallow limestone hollowing worn more than fifty million years ago by the trickling ground waters of a bygone tropic world.

The hollowed layer was not more than seven or eight feet deep but extended off indefinitely in all directions and had a fresh, slightly moving air which suggested its membership in an extensive subterranean system. Its roof and floor were abundantly equipped with large stalactites and stalagmites, some of which met in columnar form: but important above all else was the vast deposit of shells and bones, which in places nearly choked the passage. Washed down from unknown jungles of Mesozoic tree ferns and fungi, and forests of Tertiary cycads, fan palms, and primitive angiosperms, this osseous medley contained representatives of more Cretaceous, Eocene, and other animal species than the greatest paleontologist could have counted or classified in a year. Mollusks, crustacean armor, fishes, amphibians, reptiles, birds, and early mammals – great and small, known and unknown. No wonder Gedney ran back to the camp shouting, and no wonder everyone else dropped work and rushed headlong through the biting cold to where the tall derrick marked a new-found gateway to secrets of inner earth and vanished aeons.

When Lake had satisfied the first keen edge of his curiosity, he scribbled a message in his notebook and had young Moulton run back to the camp to dispatch it by wireless. This was my first word of the discovery, and it told of the identification of early shells, bones of ganoids and placoderms, remnants of labyrinthodonts and thecodonts, great mosasaur skull fragments, dinosaur vertebrae and armor plates, pterodactyl teeth and wing bones, Archaeopteryx debris, Miocene sharks’ teeth, primitive bird skulls, and other bones of archaic mammals such as palaeotheres, Xiphodons, Eohippi, Oreodons, and titanotheres. There was nothing as recent as a mastodon, elephant, true camel, deer, or bovine animal; hence Lake concluded that the last deposits had occurred during the Oligocene Age, and that the hollowed stratum had lain in its present dried, dead, and inaccessible state for at least thirty million years.