Branner.] t>±4 [Feb. 19, 



currents can hardly be regarded as evidence that there was an under-cur- 

 rent filling and flowing down the Wyoming valley, while another upper- 

 current flowed over the tops of the mountains. The existence of different 

 sets of striae in the same place, pointing one set across the mountain, and 

 another down the valley, make such a theory unnecessary at least. Evi- 

 dence that there were no great or extensive undercurrents in the ice may 

 he seen in the gap through which the Lackawanna runs at Archbald. 

 Just above the village, where the track of the D. & H. Gravity railway 

 track crosses the old plank road, the stria? show beyond question that the 

 ice in passing through this gap was not deflected by the topography into 

 undercurrents, but that it was pushed straight ahead, and when there was 

 not room for it in the narrow gorge, it was forced obliquely up and over 

 the steep side of the hill, while the main body of the ice moved square 

 across the hill that here stands out across the valley. If it had been mov- 

 ing in currents, it would have gone around the end of the hill, and the 

 striae would converge in the narrowest part of the gorge. 



Again, at Mocanaqua, a quarter of a mile from the bridge, up the railway 

 track, the striae on the red shale point up the side of the steep hill at an 

 angle of at least 30°, showing that the ice at the side of this gap flowed 

 straight forward and up the hillside, instead of turning as an undercurrent 

 and going down the channel as water would have done. 



Just east of Mocanaqua, on the top of the hill above the West End 

 breaker, a few hundred feet from it, and near the side of the road, are ex- 

 posures of striae with the following bearings : 



S. 30O E. 



S. 250 E. 



Due South. 



s. 450 W. 



S.65QW. 

 Due West. 



Those pointing S. 30° E. and S. 25° E. appear to be the oldest of the 

 ones now preserved, while those pointing due south predominate. It 

 seems probable therefore that the oldest striae were made when the ice 

 came over the Shickshinny mountains, and when it was thick enough to 

 disregard such a topographical feature. As the ice became thinner it ran 

 due south, the later striae almost obliterating those previously made. 

 Further thinning of the ice sheet subjected it more and more to local 

 influences until nothing was left here but a thin and narrow body of ice 

 that came down the valley of Black creek, and being turned by the con- 

 glomerate ledge, left these last faint striae that point west over the edge of 

 the precipice. 



In the Lackawanna end of the valley are several cases of double sets* of 



*Strise sometimes cross each other at well-defined angles without occuring in 

 sets. Such variations may possibly have been caused by the cut tins: material 

 having been turned in the grasp of the ice. No account was taken of strice of 

 this character. 



