 In autumn 1871 , Cope began prospecting farther west to the fossil fields of Kansas . Leidy and Marsh had been to the region earlier , and Cope employed one of Marsh 's guides , Benjamin Mudge , who was in want of a job . Cope 's companion Charles Sternberg described the lack of water and good food available to Cope and his helpers on these expeditions . Cope would suffer from a " severe attack of nightmare " in which " every animal of which we had found trace during the day played with him at night ... sometimes he would lose half the night in this exhausting slumber . " Nevertheless , Cope continued to lead the party from sunrise to sunset , sending letters to his wife and child describing his finds . The severe desert conditions and Cope 's habit of overworking himself till he was bedridden caught up with him , and in 1872 , he broke down from exhaustion . Cope maintained a regular pattern of summers spent prospecting and winters writing up his findings from 1871 to 1879 . 
