2 INTRODUCTION. 



Every sphere in space must have had a related system of growth, 

 and all are, in fact, individualities in this Kingdom 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 his- 

 tory. The science of minerals is more immediately important to 

 the geologist, because aggregations of minerals constitute rocks, 

 or the plastic material in which the records of the past were made. 



3. The earth, regarded as such an individuality in a world-king- 

 dom, has not only its comprehensive system of growth, in which 

 strata have been added to strata, continents and seas denned, 

 mountains reared, and valleys, rivers, and plains formed, all in 

 orderly plan, but also a system of currents in its oceans and atmo- 

 sphere, — the earth's circulating-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 meteorological 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, 



4. Three departments of science arising out of this indi- 

 vidual 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 Geo- 

 graphy) : (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. 



