66 BIOLOGICAL LECTURES. 



which the harder and softer beds alternate, their angles of 

 inclination, and the intensity and character of the denuding, 

 disintegrating agents. Most of the Tertiary formations have 

 strata which are practically horizontal, and this lack of inclina- 

 tion has a decisive influence upon the resulting topographical 

 forms. True, the western end of the White River beds is 

 some 2000 feet higher than the eastern end, but a rise of 2000 

 feet in more than 500 miles, which is an average grade of four 

 feet to the mile, or i in 1320, is so slight that it may be 

 neglected. Much more effective is the manner in which the 

 harder beds are arranged, and, as this varies indefinitely, the 

 number of resulting forms is well-nigh incalculable, though a 

 certain uniformity is apparent in the greater number of them. 



The curious aspects of bad land scenery are much enhanced 

 by the coloring. In the White River region the dreary, barren, 

 and desert character of the country is emphasized by the pale, 

 ashy gray of most of its rocks and soils, a color which the lan- 

 tern slides reproduce quite accurately. Only the marvellous 

 changes wrought by the magic touch of the tender evening 

 lights redeem the scenery from utter dreariness. In other 

 regions, as along Vermilion Creek in Wyoming, the most bril- 

 liant hues of reds and purples give an unearthly beauty to the 

 weird picture. 



In these days of evolutionary study almost as much impor- 

 tance is attached to a knowledge of the environment which 

 surrounds an organism, as to a knowledge of the organism itself, 

 and rightly so. Whether or not we follow Weismann in declar- 

 ing that acquired characters cannot be transmitted, we cannot 

 fail to see the dependence of organisms upon their environment, 

 the only question being whether the effects are directly or 

 indirectly produced. Of course, we do not hope or expect to 

 learn the environment of extinct forms with the same fullness 

 and accuracy as in the case of existing animals, but still we 

 may learn much that is of importance. We may determine 

 something of the nature of the land surfaces at the time when 

 the organisms in question existed. The new study of topog- 

 raphy, which is rapidly rising to the dignity of a distinct sci- 

 ence, gives a great deal of welcome information here. Even 



