near Mount Washington. 17 



An interesting bit of confirmatory evidence of the antiquity 

 of these valley glaciers is found in the asymmetry of the Great 

 Gulf. There is no apparent reason why a valley glacier, 

 occupying this gulf, should not have developed and left as steep 

 a wall on the southeast side as on the northwest. Supposing, 

 however, that the ravine was carved earlier in the glacial 

 period and subjected to heavy glaciation from the northwest, 

 one sees significance at once in the present lack of symmetry. 

 The ice sheet, overriding the wall on the northwest side, main- 

 tained its cliffs by plucking as on the lee side of a roche 

 moutonnee : but pushing against the wall on the southeast side, 

 it reduced its slope, and, when it melted, scattered over it 

 hundreds of blocks which it was carrying out of the gnlf. 



There can be no question, it seems to me, in view of the facts 

 outlined above, that these ravines were hollowed out by vigor- 

 ous valley glaciers before the North American ice sheet came 

 into the White Mountains. If further study should indicate 

 that the block-strewn upper floor of King Ravine, and similar 

 block deposits in the other ravines, are after all true morainic 

 deposits instead of late glacial avalanche and kame deposits, the 

 fact remains that these deposits in question occupy but the 

 upper portions of the cirques ; and the post-ice-sheet glaciers of 

 these White Mountains, at best, are scarcely a mile in length. 



It will be one of the leading problems in further work in 

 this region to determine whether the cirque-carving glaciers 

 were at work in an early stage of the last glacial epoch, while 

 the ice sheet was advancing towards the White Mountains, or 

 during an earlier glacial epoch. What took place in New 

 England during the Kansan and Illinoian epochs is still in doubt. 

 It seems not improbable that during one of these early glacial 

 epochs, say, the Kansan, the great ice sheet, spreading from the 

 more westerly Keewatin center, and advancing to its outer 

 limit in the middle west, failed to reach New England. Mean- 

 while local snowfields might have collected on the highest 

 mountains of New Hampshire and Maine, sufficiently large and 

 enduring to nourish glaciers of the Alpine type. The fact that 

 the cirques were probably not occupied at all by local glaciers 

 when the ice sheet last withdrew seems to carry with it the 

 necessity for supposing that cirque glaciers did not develop while 

 the last ice sheet was approaching. There are, however, at 

 least two ways of explaining away this objection. In the first 

 place, the change of climate which brought about the close of 

 the last glacial epoch may have been much faster than the change 

 which earlier introduced the glaciation, allowing too short a 

 time for the local snowfields and glaciers to develop. And in 

 the second place, assuming for simplicity that the oncoming of 

 the cold climate was followed by a return of the warm climate at 



Am. Jour. Sci.— Fourth Series, Vol. XXXV, No. 205.— January, 1913. 

 2 



