156 Prof. Rogers's Address before the 



The Ponent series includes all the rocks between the base of the 

 Catskill red sandstone and the top of the overlying conglomerate. (For- 

 mation X, of the Pennsylvania and Virginia annual Reports.) It usu- 

 ally embraces but two formations, the Ponent red sandstone and the 

 Ponent conglomerate, though the former of these requires for some 

 districts a triple subdivision. 



The Vespertine series comprehends the interesting formations above 

 the horizon of the Ponent conglomerate, and below that at the base of 

 the great conglomerate under the coal measures. In Pennsylvania it 

 is composed of the thick red shale deposit of the coal regions, and in 

 Virginia of a much more complex set of strata, including a lower red 

 shale or variegated marl, next a great thickness of carboniferous lime- 

 stone, and then an upper set of shales with alternating sandstones. In 

 the western states, on the other hand, it consists almost exclusively of 

 the carboniferous limestone and its subordinate chert. 



The Serai series embraces one vast and multiform body of coal 

 strata, the thickness of which in Western Pennsylvania and Virginia 

 exceeds three thousand feet, being in the anthracite basins probably 

 still greater. The lowest or oldest subdivision of this series is the Se- 

 rai conglomerate, and the true coal formation overlying this is divided 

 into four distinct members — the older coal measures, older shales, new 

 coal measures and neio shales ; these last terminating the entire suc- 

 cession of one thick and wide-spread Appalachian strata. 



The whole body of rocks here grouped into nine series, contains up- 

 on the most careful analysis which we have been able thus far to insti- 

 tute, about forty eight formations, few if any of which are co-extensive 

 with the present limits of the great Palaeozoic basin in which they lie, 

 or even with that part of it included between the Blue Ridge chain, the 

 Mississippi River, and the great Lakes. Those which were most widely 

 deposited are the Matinal magnesian limestone, the Levant older (or 

 Niagara) limestone, the Vespertine (or carboniferous) limestone, and 

 the older coal measures. Others occupy a relatively circumscribed 

 area, yet none are called formations which are not the products of dis- 

 tinct formative actions operating during epochs characterized by dis- 

 tinct groups of races. 



My brief limits will not allow me to present here even the general 

 scheme of names by which we propose to designate the divisions of 

 this extensive system of strata ; but I will explain succinctly the princi- 

 ples upon which the names are chosen. The title given to any forma- 

 tion is composed first, of the name of the jjeriod to which it appertains, 



