436 Lever ett — Observations on Craigton Lake. 



the level of the beaches near Funk and Blachleyville 765 feet 

 where it should have been 965 feet. This corrected altitude, it 

 will be observed, is within five feet of the altitude as deter- 

 mined by the present writer with topographic sheets in hand. 

 There is thus, in reality, practical agreement between us as to 

 the features which should be referred to lake action in the 

 greater part of the area of the real Craigton Lake, the only 

 point of disagreement being, as noted above, in the interpreta- 

 tion of the descent between Craigton and Custaloga, which the 

 present writer would refer to the fall of the stream instead of 

 to differential uplift. Our interpretations are, however, widely 

 different as to features farther north beyond the real lake. 



It was found that the features along the valley borders to 

 which Professor Hubbard had run lines of precise levels to 

 determine tilting, were, as had been suspected, the same fea- 

 tures which the present writer had years before classed as ice- 

 border features. They stand 30 to 50 feet or more above the 

 level of the valley bottom, and are in many cases bordered, on 

 the side toward the valley, by a slope with basins and irregulari- 

 ties, which seem to be the product of the ice edge, and to have 

 been unaffected by subsequent lake action. In some cases 

 these terraces or embankments are expanded into flats or plains 

 one-eighth mile or more in width, but usually they are only a 

 few rods wide, and are subject to frequent interruptions. Two 

 such places on the accompanying map are exceptionally 

 expanded. One about 1^ miles northwest of Craigton, marked 

 F 985 (from its altitude), covers an area of about ten acres, 

 while one a mile southeast of Blachleyville, marked F 990, 

 covers fully twenty acres. The former is closely associated with 

 a weak moraine which leads out into the valley north of Craig- 

 ton and seems likely to be due to the escape of glacial waters 

 while the ice was still occupying the moraine. In the tract 

 southeast of Blachleyville the slope toward Craigton Lake is 

 diversified with basins which seem naturally interpreted as an 

 ice-border product. Now that topographic maps are available 

 it will be possible to woi*k out an interesting detailed history of 

 the recession of small ice tongues from valleys of this sort. 

 Such a full and detailed mapping, however, was not attempted 

 at the time of the writer's recent visit, which was made merely 

 to determine the nature of the evidence in reference to differ- 

 ential uplift. 



Ann Arbor, Michigan. 



