Z INTRODUCTION. 



lated s} r stem of growth, and all are, in fact, individualities in this King- 

 dom of Worlds. 



Geology treats of the earth in this grand relation. It is as much 

 removed from Mineralogy as from Botany and Zoology. It uses all 

 these departments ; for the species under them are the objects which 

 make up the earth and enter into geological history. The science of 

 minerals is more immediately important to the geologist, because ag- 

 gregations of minerals constitute rocks, or the plastic material in which 

 the records of the past were made. 



The earth, regarded as such an individuality in a world-kingdom, 

 has not only its comprehensive system of growth, in which strata have 

 been added to strata, continents and seas defined, mountains reared, 

 and valleys, rivers, and plains formed, all in orderly plan, but also a 

 system of currents in its oceans and atmosphere, — the earth's circulat- 

 ing-system ; its equally world-wide system in the distribution of heat, 

 light, moisture and magnetism, plants and animals ; its system of 

 secular variations (daily, annual, etc.) in its climate and all meteoro- 

 logical phenomena. In these characteristics the sphere before us is 

 an individual, as much so as a crystal, or a tree ; and, to arrive at any 

 correct views on these subjects, the world must be regarded in this 

 capacity. The distribution of man and nations, and of all productions 

 that pertain to man's welfare, comes in under the same grand relation ; 

 for, in helping to carry forward man's progress as a race, the sphere is 

 working out its final purpose. 



There are, therefore, 



Three departments of science, arising out of this individual 

 capacity of the earth. 



I. Geology, which treats of (1) the earth's structure, and (2) its 

 system of development, — the last including (1) its progress in rocks, 

 lands, seas, mountains, etc. ; (2) its progress in all physical conditions, 

 as heat, moisture, etc. ; (3) its progress in life, or its vegetable and 

 animal tribes. 



II. Physiography, which begins where Geology ends, — that is, 

 with the adult or finished earth, — and treats (1) of the earth's final 

 surface-arrangements (as to its features, climates, magnetism, life, etc.) ; 

 and (2) its system of physical movements or changes (as atmospheric 

 and oceanic currents, and other secular variations in heat, moisture, 

 magnetism, etc.). 



III. The earth with reference to man (including ordinary 

 Geography) : (1) the distribution of races or nations, and of all pro- 

 ductions or conditions bearing on the welfare of man or nations ; and 

 (2) the progressive changes of races and nations. 



The first considers the structure and growth of the earth ; the 



