INTRODUCTION. 6 



second, its features and world-wide activities in its finished state ; the 

 third, the fulfillment of its purpose in man, for whose pupilage it was 

 made. 



Relation of the earth to the universe. — While recognizing the 

 earth as a sphere in a world-kingdom, it is also important to observe 

 that the earth holds a very subordinate position in the system of the 

 heavens. It is one of the smaller satellites of the sun, — its size about 

 1-1, 200, 000th that of the sun. And the planetary system to which 

 it belongs, although 3,000,000,000 of miles in radius, is but one among 

 myriads, the nearest star 7,000 times farther off than Neptune. Thus 

 it appears that the earth is a very small object in the universe. 

 Hence we naturally conclude that it is a dependent part of the 

 solar system ; that, as a satellite of the sun, in conjunction with other 

 planets, it could no more have existed before the sun, or our planetary 

 system before the universe of which it is a part, than the hand before 

 the body which it obediently attends. 



Although thus diminutive, the laws of the earth are the laws of the 

 universe. One of the fundamental laws of matter is gravitation ; and 

 this we trace not only through our planetary system, but among the 

 fixed stars, and thus know that one law pervades the universe. 



The rays of light which come in from the remote limits of space 

 are a visible declaration of unity ; for this light depends on molecular 

 vibrations, — that is, the ultimate constitution and mode of action of 

 matter; and, by the identity of its principles or laws, whatever its 

 source, it proves the essential identity of the molecules of matter. 



Meteoric stones are specimens of celestial bodies occasionally reaching 

 us from the heavens. They exemplify the same chemical and crystal- 

 lographic laws as the rocks of the earth, and have afforded no new ele- 

 ment or principle of any kind. 



The moon presents to the telescope a surface covered with the 

 craters of volcanoes, having forms that are well illustrated by some of 

 the earth's volcanoes, although of immense size. The principles ex- 

 emplified on the earth are but repeated in her satellite. 



Thus, from gravitation, light, meteorites, and the earth's satellite, we 

 learn that there is oneness of law through space. The elements may 

 differ in different systems, but it is a difference such as exists among 

 known elements, and could give us no new fundamental laws. New 

 crystalline forms might be found in the depths of space, but the laws of 

 crystallography would be the same that are displayed before us among 

 the crystals of the earth. A text-book on Crystallography, Physics, 

 or Celestial Mechanics, printed in our printing-offices, would serve for 

 the universe. The universe, if open throughout to our explorations, 

 would vastly expand our knowledge, and science might have a more 

 beautiful superstructure, but its basement-laws would be the same. 



