Rivers of Northern New Jersey. 101 
which cut the mountains in two” (152, 153). If this interpreta- 
tion is correct, the Green river would be the type of a perfect 
antecedent stream : but it appears to me that the case is proba- 
bly overstated in that respect. Perhaps it would have been 
more deliberately stated in a later volume if Powell’s intention of 
describing more fully the three chief kinds of drainage of the re- 
gion had been carried out.* Not having seen the region, my com- 
ments may have little value ; but the context of Powell’s report, 
the description of the immense series of lacustrine beds, over a 
mile thick, north of the mountains, and the eastward deflection of 
the river where it traverses the mountains all seem to me to indi- 
cate that the Green was by no means continuously successful in 
maintaining its antecedent course across the uplift. It is by no 
means a typical antecedent river. The great series of lacustrine 
beds up-stream from the canon, with conglomerates where they 
rest on the northern flank of the mountains, are fully recognized 
in the report, and must mean that the upper portion of the river 
was for a time shut back, or ponded. During part of this time, 
there may have been no overflow across the growing mountains, 
_for the lower lacustrine beds contain fossils indicative of brackish 
water.t The intermittent growth of the mountains and the re- 
peated return of lacustrine conditions, with gradually freshening 
water, is indicated by the strong unconformities that occur at 
various points in the lacustrine beds, and by the change in the 
fossil fauna. It must be conceded from this that the upper por- 
tion of Green river was repeatedly ponded back by mountain 
growth across its middle course ; we therefore have not now any 
close indication of its pre-lacustrine course above the mountains ; 
the ancient, or pre-Uinta, upper portion of the river was extin- 
guished by the lacustrine sediments, and to that extent the Green 
river departs from the perfect antecedent type. 
In the second place, if the original Green river existed upon 
the upper surface of the beds that were at a subsequent date 
raised to form the Uinta uplift, it does not appear to be clearly 
proved that its course at that early time was closely coincident 
with its present course in the mountainous area. The first de- 
formations of the mountain growth may have temporarily inter- 
rupted its flow, as is made likely by the lacustrine deposits 
* Geol. Uinta mountain, page v. 
+ Geology of the Uinta mountains, 1876, 84; Chapter III, by C. A. 
White. 
