THE LEWIS BROOKS MUSEUM. 23 



slow progress and late development of the branches of Na- 

 tural History. Only of late have they made any rapid 

 progress. 



Now as Geology makes use of, and depends upon, all 

 the departments of Natural Science, it follows that it must 

 be the last in the order of development. This science, 

 which in its broader sense may be defined to be, the physi- 

 cal history of the earth and its inhabitants, illustrates most 

 beautifully the "'unity" of Natural Science, and teaches 

 ' better than any other the great fact that there ai e no 

 sharply drawn lines of division between the departments of 

 nature. 



In our study of all the multitude of objects and phe- 

 nomena with which it deals we learn that as our means of 

 research improve the artificial barriers, erected by man to 

 aid his limited intellect, are broken down. We learn from 

 it the great plan of nature, and no more fitting motto could 

 be erected over an assemblage of her products than the 

 words : "Unity in endless diversity." 



Let us, in the first place, consider some of the relations 

 of Geology to the other branches of Natural Science. 



The forces of Physics and Chemistry find now, and 

 have found through long ages in and on the earth, a theatre 

 of action on the grandest scale. Only by observation of 

 the present changes of the earth and its belongings, can we 

 study immediately such forces. Chemical and Physical the- 

 ories are therefore Geological theories also, so closely are 

 these sciences connected. It follows from this that the 

 Chemistry and Physics of Geology are important integral 

 parts of the science. So important a part, indeed, do chem- 

 ical agencies play in the changes of the earth's component 

 parts, that such authors as Bischoff, the great German writer 

 on Chemicctl Geology, would explain all geological changes by 

 the action of chemical forces, thus erecting a universal hy- 

 pothesis on a chemical base. Inasmuch as minerals and 

 their groupings form the rocks which constitute the mass of 



