Association of American Geologists and Naturalists. Ill 



tioii in their valuable paper, the National Intelligencer — on mo- 

 tion of Mr. Sillhnan, it was resolved that the thanks of the As- 

 sociation be presented to Messrs. Gales & Seaton, and that their 

 offer be accepted. 



The order of the day was then taken up. Prof. H. D. Ro- 

 gers read a portion of his address, not read on the evening previous, 

 and also a paper, by himself and his brother Prof W. B. Rogers, 

 entitled " A system of classification and nomenclature of the pa- 

 Iccozoic rocks of the United States, with an account of their dis- 

 tribution more particularly in the Appalachian mountain chain." 



Referring to the great extent of their field operations for the last 

 eight years, which, besides the minute surveys of New Jersey, Penn- 

 sylvania and Virginia, have included a general tracing of the great 

 formations from Lake Huron to Alabama, and for great distances across 

 the chain, they called attention to the ample materials thus collected re- 

 lating to the fossils as well as the mineral character of the formations ; 

 from which, and from the data collected by others, they have framed 

 their proposed system of classification and nomenclature. They stated 

 that the great mass of strata composing what they designate as the Ap- 

 alachian system, whose aggregate thickness in some districts exceeds 

 30,000 feet, is made up of an extraordinary number of distinct forma- 

 tions, characterized by their organic remains and composition, marking 

 a long series of events and a vast lapse of time, and constituting one 

 uninterrupted succession of deposits, closely linked by an unbroken 

 sequence of animal and vegetable remains. Viewing the whole as a 

 single system, the entire record of one continuous period, they propose 

 to deduce from the study of the organic remains of the different portions 

 of this mass, aided by considerations of a mineral character, a classifi- 

 cation in harmony with the natural relationship of the different mem- 

 bers throughout the region which they occupy as to time and circum- 

 stances of origin — which, in other words, shall express the various 

 epochs and changes in their true relative importance ; and to clothe this 

 classification in language which shall at once be suggestive of these re- 

 lationships, and applicable every where throughout the vast region of 

 the Apalachian rocks. They showed that in such a system of nomen- 

 clature wisely framed, the primary idea suggested by the terms should 

 be that of the order in time of the successive formations, and that its 

 language, comprising in a symmetrical form all the wider as well as more 

 restricted groups of strata, and presenting the greater and smaller sub- 

 divisions in due subordination, should possess such pliancy as to admit 

 of expressing by some simple adjunct all the modifications of type ex- 

 hibited by particular divisions of the system in different or distant re- 



