242 Address before the Association of American Geologists. 



this interesting metal will ere long be obtained from our own 

 mountains. 



You will perceive that under the term primary rocks I have 

 included none that are fossiliferous. The latter, especially those 

 usually denominated transition, have, as is well known, an im- 

 mense developement in our country. A single vast basin, ex- 

 tending from the Apalachian chain nearly to the Rocky Moun- 

 tains, and from the centre of Alabama, in a northern direction, 

 perhaps even to the Arctic sea, not less than two thousand 

 miles long and twelve hundred broad, and consequently covering 

 about two and a half millions of square miles ; — this wide region 

 forms almost one uninterrupted deposit of older secondary or tran- 

 sition rocks ; the largest undoubtedly on the globe. Until re- 

 cently, these rocks could be described only under the vague 

 designation of graywacke. But light is beginning to shine in 

 upon the chaos. The upper member, that which embraces the 

 bituminous and anasphaltic coals of Pennsylvania, Ohio, Indiana, 

 Illinois, Michigan, and Missouri, seems now to be well identified 

 with the coal measures of Europe. This forms a convenient 

 starting point, and all that remains is to compare the groups be- 

 low the coal, with those similarly situated in other parts of the 

 world. Professors Henry D. and William B. Rogers have divi- 

 ded this vast series into twelve formations ; and these, including 

 the coal measures, which make the thirteenth formation, they 

 find to be not less than forty thousand feet thick. Whatever 

 m.ay be their views as to the identity of these groups with rocks 

 described in other parts of the world, they have refrained from 

 expressing an opinion, in their annual geological reports. But 

 other gentlemen suppose they have discovered marks of identity, 

 in respect to several of the groups, too strong to be resisted. It 

 is difficult to read the reports of the Ohio geologists, especially 

 that of Dr. Locke, and those of Dr. Houghton, Mr. Fealherston- 

 haugh, Prof Troost, and that of Dr. Owen on the mineral lands 

 of Wisconsin and Iowa, and that of Mr. Conrad on the New 

 York survey for 1841, without being convinced that the car- 

 boniferous or mountain limestone is extensively developed from 

 Pennsylvania westward at least fifteen hundred miles; while 

 here, as in England, it forms the repository of an immense accu- 

 mulation of lead ore. Mr. Taylor, I believe, first pointed out the 

 probable existence of the old red sandstone, or Devonian system, 



