110 National Geographic Magazine. 
Hayden was perhaps the first to point out in this country the 
antecedent origin of certain headwaters of the Missouri in Mon- 
tana, where the mountain ranges are frequently cut across by 
deep cafions. Amer. Journ. Science, xxxill, 1862, 305. Hayden’s 
Sixth Report, 1872 (1873), 85. 
Reference may be made also to White, Hayden’s Tenth Report, 
1876 (1878), 52; Peale, id., 167; Bechler, id., 372. General dis- 
cussion of valley making is given by Green, Geology for students 
and general readers, London, 1876 ; Hartung, Zeitschr. Gesellsch. 
f. Erdkunde, Berlin, 1878, 308. 
In spite of the early date of some of these essays, the idea of 
the antecedent origin of rivers did not gain general recognition 
and acceptance till it was strongly stated by Powell. 
