Davis and Wood.] 
378 
[Nov. 20, 
ridges, with Appalachian trend, having bold bluffs to the east, and 
gentler slopes to the west ; these slopes themselves being nearly 
baselevelled surfaces of a still earlier Triassic date ; in many ways 
like the present form of the Sierra Nevada of California, 1 although 
of not so great relief. 
13. Extent of the Schooley baselevel peneplain. The ancient base- 
level peneplain of the Highlands cannot have been limited to north- 
ern New Jersey ; it was the product of far extending as well as of 
long existing conditions ; it must have stretched beyond arbitrary 
political boundaries of which even the present natural lines are in 
good part of a date subsequent to its production. It is believed 
that the same ancient peneplain determines the general community 
of height and the prevailing level crest-line of Kittatinny mountain 
on the northwest border of New Jersey and of the associated ridge 
lines and upland surfaces of the Alleghanies and of the plateau far- 
ther west in Pennsylvania ; 2 but on this, final decision can hardly be 
reached till the Keystone state follows the example of its smaller 
neighbor and prepares a contoured map of its surface, than which 
that of no state in the country offers more interesting problems. We 
can say less of the extension of the northern part of the plain into 
New York ; but its southeastern extension across New Jersey is 
open to our investigation. 
14. The Watchung mountains. Standing on one of the front 
members of the Highlands, such as Sheep Hill, north of Boonton, 
one sees the long, even, parallel crest-lines of the Watchung moun- 
tains rising over the Triassic area to the southeast. These are the 
bevelled edges of two broad sheets of trap, intercalated in the beds of 
sandstone and shale of the Triassic formation ; their steep outcrop 
faces look to the east, and on the west their slopes descend gently 
at an angle somewhat less than the dip of the accompanying beds ; 
they are trenched at several points by water gaps, through which 
streams carry back-country drainage across them, and by notches 
or wind-gaps ; but between the gaps their crests extend in un- 
broken levels for long distances. 3 The question arises here as in 
the Highlands, under what circumstances could crest-lines as even 
1 J. LeConte, Araer. Journ. Sci., xxxii, 1886, 167; J. S. Diller, Bulletin 33, U. S. Geol. 
Survey, p. 12, 1, et seq. 
2 Corapare an essay by the senior author on the Rivers and Valleys of Pennsylvania, 
Nat. Geog. Mag., 1, 1889, 197. 
3 A view of the Watchung ridges back of Plainfield, as seen from the east, is given in 
Ann. Rep., N. J. Geol. Survey, 18S2, pi. 1. 
