THE PACKER CLAY. 287 



and over which the lake existed. This lake was 26 miles long and 9 

 w4de, W'ith a bay (in the Saucon valley) 11 by 3 miles. The Lehigh 

 flowed for 20 miles from Manch Chunk through slack water, with an 

 average Avidth of three-fourths of a mile before reaching it, and there 

 were long bays in the valleys through which Aquanchicola, Lizard, Ma- 

 honing, and Big creeks flow. Evidences of the elevation of the surface 

 are found in sudden stoppages of the lake formations at the 500-foot 

 contour at Parry ville, Bath, the west side of the divide at Stouts, and 

 the terrace at Lehighton, before named, as well as one at South Bethle- 

 hem. As the area is extensive, there may exist many more evidences 

 not yet discovered ; but sufficient work has been done to prove the ex- 

 istence of the lake. This varied in size and depth from two causes : the 

 occupation of a variable portion of its bottom by the glacier, and the 

 variation in the ease of drainage. There were two lake periods, and only 

 the latter has left any traces. When the glacier advanced to the mouth 

 of the Lehigh it began to form a dam under which the water escaped, 

 and as it advanced subglacial drainage became more and more difficult. 

 In time the ice filled the l:)ottom of the lake and crossed the Topton 

 divide and the first period came to an end. The second began when the 

 ice retreated across the same divide, and continued till it had freed the 

 mouth of the Lehigh. In both periods there was generall}^ slack water 

 upon wliich floated the bergs from the ice-foot, and in which settled the 

 debris lu'ouglit down by sul)glacial streams and l)ergs. During the first 

 period the lake was a cat(;h-l)asin to accumulate, on its old preglacial 

 ])ottom, a mass of clays and sands which were scraped from the decom- 

 posed soils north of the Blue ridge and at that time covered by the ice, and 

 mixed with a huge l)ulk of river and glacial gravels brought down by the 

 Leliigh, whose drainage area was crossed by fifty miles of the ice-front.' 

 The advancing ice ploughed into this mass and forced it up the southern 

 shores of the lake and over the eastern part of the Archean highlands to 

 form thick beds of till which will be described later. The water was 150 

 feet deep over Bethlehem hill, and 280 feet over the Lehigh, so that the 

 buoyant eff'ect on the glacier was great and the corresponding erosion 

 diminislied. We find deep remnants of decomposed rock at Bethlehem 

 and South Bethlehem due to this cause. The evidences of this first pe- 

 riod are, consequently, wanting, and we find only the accumulations dur- 

 ing the retreat of the ice. 



The Packer clay is, therefore, a local deposit existing between Easton 

 and the Topton divide and beloAV the level of 500 feet, with the excep- 

 tion of the part of the Saucon valley west and south of Hellertown. 

 Here tliere is no cap over the till, and this absence proves the previous 

 statement that the Leithsville divide w^as higher than that at Topton at 



