POPULAR EXPLANATION. 13 



The scientific reader is able to select from the text such 

 matters as are of especial use to him without the necessity of 

 any explanation of the principles by which they are deter- 

 mined, but considering the fact that only a few years ago 

 geology was not made a part of even a liberal education, and 

 keeping in view also the further fact that this report is ordered 

 by, and intended for the use of the people, it is thought advis- 

 able to give a brief popular explanation of its principles in 

 this introductory chapter. 



Even if these circumstances did not exist, it is always the 

 case, that to draw correct inferences from a writer's statements 

 the reader must have a clear understanding of the theories 

 upon which he bases his opinions, and through the medium 

 of which he observes his facts. In addition to this it is in- 

 tended that the subject-matter of the whole report shall be as 

 free as practicable from technical terms, as the law requires, 

 and that it shall be so arranged by sub-headings that no one 

 will have much difficulty in selecting such matters as he may 

 particularly desire, without being obliged to search through 

 those portions which may not then be of so immediate im- 

 portance. 



Rocks in general may be designated as stratified and un- 

 stratified ; or in other words, such as lie in more or less regular 

 layers and such as present no indication of layers ; being 

 .composed of a more or less granular or crystaline mass 

 throughout, and which may usually be broken and wrought 

 in one direction as well as another. Of the latter, granite 

 may be taken as the type and most common example, while 

 of the former, the varieties are very numerous, embracing all 

 the common limestones, sandstones, shales, &c. The term 

 rock is used by geologists irrespective of the hardness of the 

 substance composing it. Thus any regular beds of clay, 

 sand, shale, marl, &c, come under the same general designa- 

 tion of rocks that limestone, sandstone, and granite do. 

 Even coal, since it lies in continuous beds parallel with strata 

 that both underlie and overlie it, is itself a stratified rock, 

 geologically considered. Of the unstratified rocks, we have 



