BY PROF. DAVID, RICHARD HELMS, AND E. F. PITTMAN. 43 



and is deeply grooved, the grooves running in perfectly straight 

 lines across the platform in a direction E. 15° N. They are 

 nearly at right angles to the gneissic structure of the granite, 

 and many of them are at least 50 feet in length, and are cut to 

 a depth of one-half to one inch. These grooves form the most incon- 

 trovertible evidence as to the grinding action of moving glacier 

 ice. If the observer sights along these grooves in a direction 

 E. 15° N. he will see that they point direct to the large polished 

 roche moutonnee on the west shore of Lake Albina, near its 

 southern end, at the point where the lake is so contracted as to be 

 almost divided into two. This beautiful grooved pavement had 

 to be photographed by one of us under rather disadvantageous 

 circumstances, as the sun was shining straight down the grooves, 

 so that they cast scarcely any shadow. The photograph never- 

 theless gives a fair idea of what part of the pavement is like 

 (Plate X., fig. 1) ; the pavement must, however, be seen in order 

 to be properly appreciated. The surface is slightly weathered, 

 just sufficiently so to remove the striae, while the deep groo\'es, 

 and even some of the shallower, are retained. One very large 

 groove was observed to trend E. 33° N., thus making an angle of 

 about 16° with the general trend of the grooves on the west side 

 of Lake Albina Valley, viz., E. 17° N. 



Some of the larger grooves every here and there showed traces 

 of having been slightly pitted as though the block of rock, which 

 acted as the graving tool, had dug in more deeply at such points, 

 joggling as a chisel sometimes does in planing iron. 



Nowhere, in the part of the Kosciusko Plateau visited by us, 

 was the intenseness of the glaciation more apparent than in this 

 Lake Albina Yalle}^, it being obvious that the ice not only 

 furrowed out the bottom of the valley, but that it moved in thick, 

 heavy masses over the top of the high- ridge separating the Lake 

 Albina Valley from the Wilkinson Valley. The minimum thick- 

 ness of the ice in the Lake Albina Valley may be estimated from 

 the difference in level between Lake Albina and the top of the 

 glaciated ridge to the west of it. Lake Albina being about 6,340 

 feet above the sea, and the top of the ridge 6,850 feet; the ice in 



