200 National Geographic Magazine 



-11 



i« 



them in the paper by McGee, above 



referred to. It is proper that I should 



11 '^"'^ ^^^ tbat the suggestion of baselevel- 



ling both of the crest-lines and of the 



lowlands, that I have foiind so proiit- 



sf: -i|fl ^-ble in this and other work, is due 



largely to personal conference with 

 Messrs. Gilbert and McGee of the Ge- 

 ological Survey ; but it is not desired 

 to make them in any way responsible 

 for the statements here given. 



14. Illustrations of Pennsylvanian 



topography. — A few sketches made 



during a recent recess-trip with several 



students through Pennsylvania may 



= S. " ""-=. -^*^^-' be introduced in this connection. The 



first, fig. 4, is a view from Jenny 



Jump mountain, on the northwestern 



side of the New Jersey highlands, 



I / ^ / % i \,'>--. ""^^"^^^^j- looking northwest across the Kitta- 



tinny valley-lowland to Blue or Kit- 



tatinny mountain, where it is cut at 



the Delaware Water-gap. The extra- 



^•:^^W ^:J \^ ordinarily level crest of the mountain 



* Il4 .ST^i preserves record of the Cretaceous 



-/'// -'V^ baselevel lowland ; since the elevation 



-r'' r ^5/i' of this ancient lowland, its softer rocks 



' ./ "^^^y, have, as it were, been etched out, 



" -Jsv leaving the harder ones in relief ; thus 



-''•^^^1^ the present valley-lowland is to be 



^'^. explained. In consequence of the still 



later elevation of less amount, the 



Delaware has cut a trench in the 



S, present lowland, which is partly seen 



;. "V/" Jb^^. to the left in the sketch. Fig. 5 is a 



J V'ir ^^t general view of the Lehigh plateau 



I :' ::- ^"^P and canon, looking south from Bald 



• j "'^?j Mountain just above Penn Haven 



7 '~^^ Junction. Blue mountain is the most 



-j^^3 distant crest, seen for a little space. 



_^^>.'- The ridges near and above Mauch 



FiQ 5 Chunk form the other outlines ; all 





