DESCRIPTIONS OF THE GEOLOGICAL FORMATIONS. 



INTENDED FOR RAILWAY TRAVELERS WHO ARE NOT VERSED IN 



GEOLOGY. 



All the rock-formations which appear on the surface of the globe, have been 

 scientifically classified by geologists, according to the order in which they are 

 found lying one upon another, and by the fossils they contain, and for our object 

 may be conveniently included in twenty divisions or groups. In this work, the 

 table of the names of the formations, groups and systems, published by Prof. J. D. 

 Dana in his "Manual of Geology" and in his " Text Book of Geology," has been 

 taken as the general basis, by the geologists of many of the states who have 

 assisted in preparing the following guide, but other valuable tables and especially 

 one arranged by Dr. T. Sterry Hunt, preceding the chapter on Canada, and a 

 list for each state at the beginning of the proper chapter, are also given. Numbers 

 are attached to the names of the groups wherever they occur, making 20 in all. 

 The subordinate members of each group, which are called formations, have the 

 same number, but these sub-divisions are distinguished by the addition of small 

 letters, a, b, c, etc., thus making in all 40 sub-divisions. By this means, the reader, 

 although not familiar with geological tables, is at once enabled to see to what part 

 of the general series any formation belongs, number 1 designating the oldest 

 and number 20 the upper and last formed of all. Wherever the formations are 

 found, they occur in the order as they are numbered, but the series in nature is 

 never full, and in almost every locality one or more members of it are wanting. 



The true method by which each of the great stratified formations is distinguished 

 is by its own characteristic fossils, but these descriptions, having been prepared for 

 travelers, are confined to the general aspect of the rocks as seen in passing them on 

 the railways. They are intended to be popular rather than scientific, informing the 

 reader what the formations are, what they look like, and their useful and valuable 

 characters, qualities, and productions. It must also be borne in mind that this is a 

 country of vast dimensions, and that the formations undergo important changes in 

 their lithological character from place to place. 



Paleontology, and other interesting branches constituting the purely technical 

 portion of the subject, are omitted. That ground has been well covered 

 by all of the excellent illustrated text-books on geology, and one object of 

 this work is to induce persons to take up their study. Results only are here given, 

 not the method, by which they are attained. The thicknesses of the formations are 

 sometimes stated, but as this might mislead the unprofessional reader, it should be 

 observed, that the width of the surface occupied by a formation depends on the 

 amount of dip in the beds. A group less than a hundred feet thick, lying 

 horizontally, may cover several miles, while one of several thousand feet thick, if 

 lying at a high angle, is goon passed over. 



