124 Traxsactions of the American Ixstitute. 



during successive periods, successive creations, flora after flora, each 

 more beautiful and more perfect tlian its predecessor, appear upon 

 the surface of the planet. Then again comes the zoologist, who 

 investigates the various forms of animal life. All these ages, beauti- 

 ful and important as they are, are mere hand-maidens to that great 

 complex study which we call geology. Prof, Hunt said he would 

 merely discuss the chemical relations of our globe, but he must to a 

 certain extent go outside of our globe, because we must look at it 

 from the astronomer's point of view. The chemist had to look to the 

 rocks, the waters, and the air but behind all these came in another 

 question, whence was the origin of rocks, or water, and of air ? 

 There must have been a time when these were not, and the first 

 question of the student was as to the origin of these things. It was 

 the rare privilege of the scientific eye to look backward, to solve this 

 problem, and to learn as it were, the history of these pre-historic 

 times. To the astronomer, wlio recognized the fact that our globe 

 was but one of many worlds, there came in a strange and unexpected 

 light to aid us, and physical science here contributed most curious 

 stores of knowledge. Speculating upon the origin of our earth, and 

 seeijig the curious harmony which existed between its motions and those 

 of its satellites, and of the other planets that moved around the sun, the 

 great Kant was induced to ascribe a unity of origin to all. Later, the 

 idea was developed by La Place, who supposed that from a great nebu- 

 lous cloud existing in space there was formed, in accordance with cer- 

 tain physical laws, successive planets successive satellites, the sun finally 

 remaininof in the center, the whole the condensation of one innnense 

 cloud of vapor, for whose origin still further back we must only look 

 to the great Author of existence, who created it and imposed upon 

 it the laws which, in after ages, regulated its development. Tliis 

 great nebulous cloud rested in this condition until Sir Wm. Ilcrscliel, 

 in studying the skies, detected certain masses of light whicli had 

 before been known as certain cloudy, milky masses of white light. 

 He viewed them with his great telescope, and was unable to resolve 

 them. Here he said, "I have the origin of this cosmic matter; here 

 I really see the stuff of Avhich worlds are made," and he described 

 them as so many nebulae. Later astronomers looked at the matter 

 with more powerful glasses and were able to resolve many of them 

 into groups of stars. For instance, the great milky-way, which we 

 observed so plainly in a clear, cold winter's night, was found, on 

 close examination, to be made almost entirely of little stars, which 



