GLACIAL PHENOMENA. 289 



the moraine represents the next formation above the clay as truly as if 

 d-eposited as its cap. 



The high state of oxidation of the clay has been adduced as evidence 

 of its great age, but the argument is worthless in view of the manner in 

 which it was accumulated and the condition of the burden it carries. 

 These glaciated, rolled and angular stones are generally fresh and un- 

 oxidized, as just described. We have, therefore, a highly oxidized clay 

 throughout, bearing at all levels fresh material. The mixture is no older 

 than the fresh part, and the oxidation of the clay is either preglacial, 

 from its having been part of the soil of the region (as gneiss, limestone 

 and slate all rot to just such a cla}^, or due to oxidation while it was 

 being deposited. Judging from the state of certain portions of the till, the 

 chances are in favor of the former supposition. These fresh fragments an- 

 tedate the great moraine and show that it also is of recent date. It mav 

 ))e argued that tlie clay is the ordinary 1)0 wider-clay of subgiacial origin. 

 If it Avere its deposition would have disturbed the stratification of the 

 underlying gravels and sands, and there would not be the great propor- 

 tion of angular fragments in the burden, nor, further, would we in hun- 

 dreds of cases find the till shading graduallv and conformably into the 

 overlying cla}'. 



Drumlins, Karnes and other glacial Phenomena. — As the clay cap hides 

 the greater ])art of the region, except where cuts have been made, few 

 buried deposits of the types specified have been found. It has not been 

 fully determined wliether tlie ridges of unstratified gravel at Bingen, 

 Siegfried, Nortliampton, etcetera, are drumlins or portions of lateral or 

 terminal moraines. The two latter deposits are on the north bank of the 

 Lehigh and are 10 to 20 feet tliick, from lialf a mile to one mile long, 

 and from a few hundred feet to lialf a mile wide. The chances are in 

 favor of their being drumlins and connected with the subgiacial drainage 

 of the region. 



Ranch's gravel pit at West Bethlehem is a stratified (plunge and flow) 

 deposit varying in thickness from a few inches to 30 feet, as far as known. 

 Its thickness may be greater to the west, and it pinches out to the east 

 and south by the erosion of its surface, and to the north by the rising of 

 the underlying rock. The clay cap is continuous over the whole, but is 

 twice as thick at the western end, so that both deposits seem to have 

 been influenced by similar forces, but at different times, as the clay is 

 unconformable. Plate 10 shows the central third of the north face of 

 Ranch's pit. The unconformity l)etween the clay cap and the gravel is 

 ])lainly marked, as well as the thinning of the dej^osit toward the east. 

 Tlie darker smooth surface over which the lower end of the tape lies is the 

 glaciated remnant of decomposed calciferous sandstone that preglacially 



XL— Bui.r,. Geoi,. Soc. Am., Voi,. 5, 1893. 



