 Throughout the decade , Cope traveled across the West , exploring rocks of the Eocene in 1872 and the Titanothere Beds of Colorado in 1873 . In 1874 , Cope was employed with the Wheeler survey , a group of surveys led by George Montague Wheeler that mapped parts of the United States west of the 100th meridian . The survey traveled through New Mexico , whose Puerco formations , he wrote to his father , provided " the most important find in geology I have ever made " . The New Mexico bluffs contained millions of years of formation and subsequent deformation , and were in an area which had not been visited by Leidy or Marsh . Being part of the survey had other advantages ; Cope was able to draw on fort commissaries and defray publishing costs . While there was no salary , his findings would be published in the annual reports the surveys printed . Cope brought Annie and Julia along on one such survey , and rented a house for them at Fort Bridger , but he spent more of his own money on these survey trips than he would have liked . 
