. The pictorial sketch-book of Pennsylvania, or, Its scenery, internal improvements, resources, and agriculture, populary described . g. 40. The con-formable or unconformable posi-tion of the strata affords a safe fig. satisfactory guide to many investigations of interest and great practical importance. Fromdata thus furnished, we learn that the mountain-chains were not allof contemporaneous origin, but have been raised at different periods,and sometimes under different circumstances and agencies. Thus,if on the sides of one mountain, fig. 41, we find a series of strata, a,raised and co
. The pictorial sketch-book of Pennsylvania, or, Its scenery, internal improvements, resources, and agriculture, populary described . g. 40. The con-formable or unconformable posi-tion of the strata affords a safe fig. satisfactory guide to many investigations of interest and great practical importance. Fromdata thus furnished, we learn that the mountain-chains were not allof contemporaneous origin, but have been raised at different periods,and sometimes under different circumstances and agencies. Thus,if on the sides of one mountain, fig. 41, we find a series of strata, a,raised and covered unconformably by another group, b, it is obviousthat the central chain must have been thrown up aflcr the scries ahad been dr-positcd, but Ufore the formation of the beds b. But if,on the sides of another mountain, fig. 42, we find both the series aand b tilted, and covered unconformably by another series c, we haveproofs thai ihiH mountain chain is of more modern date than that onthe sides of which the same strata, b, are undisturbed. We have already remarked, that in all mineral regions, and espe- 152 OFF-HAND FIG. 41. cially in that of coal, where the basins are generally more or lessdisturbed—as, from the very nature of the deposit, they must be—the dip and strike of the strata are matters of great practical Richardson, in his geological work, supposes a case, where aland-owner, aware that coal exists on an adjacent estate, is desirous
Size: 2803px × 892px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade, booksubjectminesandmineralresources
