Prof. G. S. Hitchcock — Glacial Period in E. America. 249 



observed striation is at right angles to this south-east course, and 

 travelled directly over the highest ridges and summits towards the 

 sea. I find upon the summit of Mount Washington boulders weigh- 

 ing 90 lbs. that have travelled certainly ten miles and ascended as 

 much as 4000 feet above their source. I also find stria? and ' till ' 

 there. Heretofore the top of this mountain, 6291 feet above the sea, 

 has been regarded as a glacial island. 



2. In the decline of the ice period local glaciers radiated from the 

 White and Green Mountains. Those passing southerly were the 

 most conspicuous. Their traces consist partly of stria?, and, in their 

 absence, of transported material. Careful preliminary studies of the 

 position of the several formations has made such identification 

 possible. 



3. The till consists of two parts, called lower and upper, and 

 believed to be the equivalents of the corresponding parts of the till of 

 the British Islands. The lower consists of bluish compact earth 

 containing small striated and far-travelled boulders, with occasional 

 lenticular gravel sheets. Its iron oxide is mostly ferrous, the same 

 as that of the rocks before transportation. The upper till is 

 universal; is a reddish-brown loose material with imbedded and 

 overlying rough blocks of large size which have usually travelled a 

 short distance. The iron oxide is hydrous ferric. The description 

 of the common varieties of the Scottish till, by James Geikie, in the 

 Great Ice Age, second edition, p. 116, seems to agree with this. All 

 these facts, especially the condition of the iron oxide, necessitates 

 the belief that our lower till is the proper ground moraine, while the 

 upper till consists of all the ice-borne materials (lateral, median and 

 much of the terminal moraines with imbedded detritus), which fell 

 upon the subjacent hard face when the ice melted. The upper till 

 would therefore cover the lower deposit uniformly and universally, 

 save where enormously accumulated in the terminal or frontal 

 moraines ; and the original anhydrous ferrous oxides would absorb 

 water and oxygen by exposure to air and water during the melting 

 process. Careful analyses confirm our impression of this diverse 

 nature of the iron oxides. 



4. No facts seen confirm the theory of the presence of a 

 universal interglacial warmer period. The few marine beds lying 

 between the two tills contain boreal fossils, or the remains of such 

 animals as now flourish in Greenland, and they are covered only by 

 our upper till. A true ground moraine never overlies the inter- 

 glacial beds. An excellent case may be seen at Portland, Maine, where 

 we find, first, enormous deposits of lower till ; second, marine beds 

 (called Champlain) containing 121 species of fossils, reaching to 100 

 feet above the present sea-level, thus indicating a submergence of 

 that amount; third, deposits of upper till, 25 feet thick, covering 

 uniformly both the lower till and the marine beds. Eecent excava- 

 tions made in grading the streets show these facts incontestably. 

 Hence it seems plain that for a brief period the glacier retreated a 

 short distance, allowing the marine beds to accumulate just as they 

 do now in Greenland ; then the ice re-advanced so as to cover the 



