Geological Society. 527 



the condition which its soil derives from the rocks or strata that 

 have supplied the materials of which it is composed ; and wisely 

 profiting by his suggestions, the diflFerent governments of the United 

 States have caused geological surveys to be made of their respective 

 districts; fully aware that not only the agricultural condition of 

 every country must depend on the nature of its soil ; but its future 

 capabilities of becoming the site of extensive manufactures must 

 also mainly depend on the presence or absence of subterraneous 

 stores of fossil fuel. 



Mr. Maclure's publications upon the geology of this most import- 

 ant part of the Western Hemisphere are marked with the finest ap- 

 preciation of the just philosophical principles of geological research, 

 and a spirit of combination and generalization of the largest and 

 boldest character, yet never running wild. His map, which pre- 

 sents the synoptical result of the whole, is unrivalled by anything 

 produced before that time. Adopting the Wernerian arrange- 

 ment, he is far superior to Werner in the philosophical character of 

 his mind ; his colours represent primitive, transition, secondary, 

 and what he calls alluvial, which are mostly tertiary, on the east of 

 the Alleghany chain. Under this class he has included the lower 

 cretaceous formations of New Jersey, which he remarks may pro- 

 bably prove to be secondary. The'great simplicity of the struc- 

 ture of America, and more extensive continuity of its formations 

 as compared with those of Europe, greatly facilitated his task ; his 

 map is therefore a very near general approximation to what would 

 even now be given ; his secondary rocks include what would now 

 be called Silurian and Carboniferous, and he notices the absence of 

 the chalk of Europe and of the Jura limestones. Of course he 

 could not enter into the distributions of the Silurian and Carboni- 

 ferous groups ; but he observes, that a red sandstone seems the 

 basis of the whole, and this he calls old red. The more exact local 

 description of portions of the Carboniferous and Silurian groups, 

 and the identification of the lower cretaceous deposits of greensand 

 in New Jersey and skirting the Mississippi belowthe junction of the 

 Ohio, are the principal materials of importance which have subse- 

 quently been added to his spirited and masterly original sketch. 

 His introductory remarks show tiiat he was equally well acquainted 

 with the general outline of the geology of Europe. 



He declines entering on the subject of organic remains, not as 

 unaware of its importance, but because they " had not yet been ex- 

 amined." In his preface occur some remarks which may show how 

 unjustly the earlier geologists have been charged with too great in- 

 clination to depart from tlie ordinary laws of nature : " In all specu- 

 lations on the origin, or agents, whicii have produced the changes 

 on this globe, we ought," Ik; says, " to keep within the boundaries 

 of tlie probable cfi'(;cLs resulting from the regular operations of 

 the great laws of nature, which our experience or observation has 

 brought within the sjihere of our knowledge." It is remarkable 

 that Mr. Maclure mentions galvanism as an agent which may have 

 co-operated in changing and metallizing rocks : " A galvanic pile," 



