178 Association of American Geologists and Naturalists. 
axes ; increasing interval between the axes as we advance towards the 
northwest. , 
5th. Descriptions of a series of sections across the chain, with a 
table of the northwest and southeast dips which they disclose. 
Part II, treats of the following theoretical topics : 
Ist. The force producing the flexure and elevation of the strata, 
was compounded of a wave-like oscillation of the crust, and a tangen- 
tial pressure towards the northwest. 
2nd. Theory of the origin of the supposed subterranean undula- 
tions, and of the manner in which the strata became permanently bent. 
3rd. Identity of the undulations of the crust with the wave-like mo- 
tion of the earth in earthquakes. This latter shown to result from an 
actual billowy oscillation of the surface of the subterranean fluid lava. 
4th. Of the geological era of the elevation of the hppa 
chain 
Sth. Analogous phenomena of flexures ; axes in ates countries. | 
A paper was next read by Prof. Henry D. Rogers, entitled 
“an Inquiry into the Origin of the Appalachian coal strata, bitu- 
minous and anthracite.” It embraces the following subjects : 
Ist. A brief introductory sketch of the researches of — geolo- 
gists in the same region 
Qnd. The extent ‘iad physical features of the pegsonvisane coal 
region. 
The character of the strata ; (a,) rocks. of mechanical or ter- 
vectiial origin; the laws of their gyiddittion and distribution; (4,) rocks 
of chemical or marine origin, as limestones, &e. ; the law of their dis- 
tribution ; inferences ripe Pale the position of the ancient carbonifer- 
ous sea and its coast 
4th. Of the coal seams, and the phenomena, immediately eonnect- 
ed with them ; wide range of some of the beds ; identified from basin 
to basin ; ancient limits of the coal much more extensive ; area of the 
oo Pittsburgh seam, and law of its distribution; present and former 
areas of the coal strata computed. 
5th. mi the. intimate mechanical structure of the coal ; inferences 
et. ue 
