Notes on Ameiican Geology. 249 



tinctly, that it is very easy to estimate the comparative force of 

 currents on different strata by the larger or smaller undulations 

 they have left behind. One can form an idea of the extent of 

 one of these ancient floors of the ocean, when he sees the ripple 

 marks, the same rock in mineral composition, and the same or- 

 ganic remains in Germany or Wales that he finds in New York ; 

 and can imagine how mighty a revolution the crust of the globe 

 must have undergone to gain the vast depth of the Atlantic and 

 the elevation of the Andes. 



While on the subject of the transition, it may be useful to in- 

 quire into the relative position of a sandstone which seems at 

 present little understood. It appears on the Hudson, near New- 

 burg, and passes under the Palisadoes, reappears in New Jersey 

 and Pennsylvania, following the course of the Delaware a dis- 

 tance of many miles, and disappears near Trenton, in New Jer- 

 sey, where it rests unconformably upon gneiss. The color of 

 this rock is generally red, very often with pale waved and con- 

 centric stripes ; organic remains are very rare, one or two species 

 of fucoids being all that I could find, and they differ from those 

 of any other formation. This sandstone has sometimes been con- 

 founded with that of Western New York, a gross error, arising 

 from its general resemblance to the latter. Mr. M'Clure regards 

 it as a distinct formation, but terms it old red sandstone. It ap- 

 pears to me to be intimately connected with the Hudson river 

 slaty graywacke, probably one passing into the other ; but at all 

 events it alternates with Eaton's calciferons sandrock near Easton, 

 a character which identifies it at once with the Potsdam and Es- 

 sex sandstone, described by Professor Emmons as occurring in 

 the northeastern section of New York. In all cases it rests upon 

 primary rocks and is the oldest of the fossilliferons formations, 

 being under the calciferons sandrock, and occupying the same 

 position in the geological series as the Cambrian system of Wales, 

 described by Mr. Sedgwick. The copper mines of Flemington, 

 in New Jersey, belong to this formation. The harder layers 

 make excellent building stone, and of this rock the Penitentiary 

 near Trenton is constructed. In New York it is one of the most 

 common materials for door steps and basements, and it is occa- 

 sionally used as a building material in Philadelphia, where it is 

 brought down the Schuylkill river. 



Vol. XXXV.— No. 2. 33 



