1889.] Methods and Models in Geographic Teaching. 569 
the study of biology, one may see the strongest contrast with the 
older methods in this respect. I should be glad to see a similar 
change overtake the conservative science to which my studies are 
devoted. 
In order to give specific illustration of the method of study by 
geographical types and the use of models, let me ask your con- 
sideration of that large group of land-forms that may be included 
in the category of plains, plateaus, and other derivatives. There 
is a brief preliminary consideration. 
Any mass of land constituting a single geographic individual 
or a natural group of such individuals, must, as soon as it is 
exposed to the destructive forces of the atmosphere, begin its long 
sequence of development ; and if no change of level happen to it, 
It must at length be worn down smooth and low to a featureless 
plain. When this work begins, with every mark of immaturity 
in its small accomplishment, we may regard the individual as 
young ; that is, but little advanced in the long cycle of systematic 
change through which it is destined to pass. When much more 
work has been accomplished, and the variety of form resulting is 
at its greatest, the individual may be called mature ; and finally, 
when the features of maturity weaken as the relief is reduced and 
intensity of form is lost, we find a resemblance to organic decay, 
and are warranted in the use of such a term as old age.' 
But you may say that all this is geology, not geography. 
Geological processes are indeed at work in carrying the geo- 
graphic individual through its successive forms, but we are not 
concerned with the processes, only with the results. In organic 
growth, the process is chemical ; but for all that, biology is not 
chemistry. Moreover, if the several forms assumed by a geo- 
graphic individual are geological affairs, we might expect to find 
them treated in the standard works on that science, but, except in 
brief outline, nowhere do they appear in such books. Geology 
is quite enough occupied with matters of undergro 
