rnR RELATIOKS OF GEOLOGY. 369 



with many other .sciences, especially with the science of geography. 

 Perhaps the shortest detinition that has been made of our science, and 

 one equally acceptable to its students and to those who view it from 

 the outside, is that geology is the "science of the structure of the 

 earth. It is in and around that earth structure that all geological 

 ideas center. In working out the solutions of the problems presented 

 l)y that structure, geology not only finds her own special and peculiar 

 mission, but extends a hand to all her sister sciences. 



In studying the solid elements of that structure, geology shades 

 through the science of mineralogy into that of chemistry. In the 

 study of the changes which the parts of tliat structure have undergone 

 and are now imdergoing it shades through the science of meteorology 

 into that of physics. In the study of the successive surfaces of that 

 structure it grades into the science of geography. In the study of the 

 stony relics of the vanished beings that once dwelt upon those surfaces 

 it joins hands with the sciences of zoolog}^ and botany. In studying 

 the phenomena presented by the sequence and interrelations of the 

 rock formations which go to the building up of that structure, it finds 

 the means of reading the past history of the earth and its living 

 inhabitants— a glory reserved for geology alone. 



It was not until geologists discovered that the solid earth crust had 

 a structure which was made up of definite parts or "formations" capa- 

 ble of individual recognition and description, each showing a special 

 distril^ution in space and in time, and each marked by characteristic 

 features capable of being compared, contrasted, and reasoned about, 

 that the science of geology attained individuality and became worthy of 

 its name. It was this discover}^ — inaugurated by Lehmann and Guet- 

 tard about the middle of the eighteenth century, made famous by 

 Werner and his contemporaries toward its close, and established be- 

 yond all dispute by William Smith at the dawn of the next — that gave 

 geology a claim to be regarded as one of the concrete sciences, and 

 placed in her hands the weapons with which she has fought her way 

 onward irresistibly to the conquest of her kingdom. 



Since the days of William Smith, the careful investigation and 

 mapping out of these geological formations, igneous as well as aqueous, 

 has spread outward from the original centers of investigation with 

 extraordinary rapidity, until at the present day there is hardly a 

 civilized nation that does not possess a government geological surve3\ 

 The fascinating problems presented by these formations and the light 

 which their solution has thrown upon all that concerns the past 

 development of the earth and of its living inhabitants, have not only 

 attracted hosts of enthusiastic students to the science itself, but have 

 given it a far-reaching interest to countless workers in other branches 

 of knowledge and opinion. As a consequence, there is hardly a single 

 important intellectual center in the Old World or the New whith has 



