GENETIC CLASSIFICATION OF PHENOMENA 813 
their behavior under different physical conditions, it is found 
that, broadly speaking, they are acted upon in four very distinct 
ways: (1) Ina most comprehensive manner all the rocks of 
the globe act asa unit, and are affected as such by only the 
cosmical forces. They are then considered in their astral rela- 
tions. (2) Again, physical forces may affect rocks as great 
bodies, masses or formations. This may be regarded as their 
corporeal aspect. (3) Rocks may also be influenced only as 
particles. They are then treated of in their molar relations. 
(4) Finally, rocks are changed by the motions of their mole- 
cules and atoms. The molecular agencies, as understood in this 
connection, are those commonly termed physical (in its most 
limited sense) and chemical. Since, for geological purposes, it 
is hardly necessary to make any distinction between the two 
processes of this class, both are called molecular. 
Each of the main groups, or kinds of geological processes, 
has its several minor categories, and each of these its particular 
phases. Activity of the subordinate agencies as comprehended 
under the latter give rise to the various classes of geological 
structure and geographic form. 
While a complete arrangement of all geological phenomena, 
according to the plan suggested, would necessarily require a 
critical inquiry into the whole subject of geology, some of the 
principal features of such a genetic scheme may be indicated by 
the accompanying outline. 
From this arrangement may be readily inferred many of the 
shortcomings of our existing systems. Two points are also 
prominently brought out. One is the frequent origin of very 
similar products through the action of diverse processes. The 
other is the complicated nature of most of the agencies that 
we commonly regard as simple. The absolute necessity is 
thus shown for a new series of brief, self-explanatory terms that 
will enable us to express with exactness the various processes 
according to the modern view or modified conceptions. 
In enumerating some-~of the chief processes affecting the 
rocks a number of familiar terms do not appear. Among these 
