Ill 



A CENTURY OF GEOLOGY __ STEPS OF PROG- 



RESS IN THE INTERPRETATION OF 



LAND FORMS 



By HERBERT E. GREGORY 



r~plHE essence of physiography is the belief that land 

 forms represent merely a stage in the orderly devel- 

 1 opment of the earth's surface features; that the 

 various dynamic agents perform their characteristic work 

 throughout all geologic time. The formulation of prin- 

 ciple and processes of earth sculpture was, therefore, 

 impossible on the hypothesis of a ready-made earth 

 whose features were substantially unchangeable, except 

 when modified by catastrophic processes. In 1821, J. W. 

 Wilson wrote in the Journal : * * Is it not the best theory 

 of the earth, that the Creator, in the beginning, at least 

 at the general deluge, formed it with all its present grand 

 characteristic features!" 1 If so, a search for causes is 

 futile, and the study of the work performed by streams 

 and glaciers and wind is unprofitable. The belief in the 

 Deluge as the one great geological event in the history of 

 the earth has brought it about that the speculations of 

 Aristotle, Herodotus, Strabo, and Ovid, and the illus- 

 trious Arab, Avicenna (980-1037), unchecked by appeal 

 to facts but also unopposed by priesthood or popular 

 prejudice, are nearer to the truth than the intolerant con- 

 troversial writings of the intellectual leaders whose 

 touchstone was orthodoxy. A few thinkers of the six- 

 teenth century revolted against the interminable repeti- 

 tion of error, and Peter Severinus (1571) advised his 

 students: "Burn up your books . . . buy yourselves 

 stout shoes, get away to the mountains, search the valleys, 

 the deserts, the shores of the seas. ... In this way and no 



