CENOZOIC TIME — QUATERNARY. 959 



that clay makes a part of till, and sometimes interlaminating beds ; and that 

 half-decomposed rock-flour, fitted to make loess, should have been contributed 

 so abundantly to the Mississippi and its tributaries. 



The smaller traveled stones were sometimes ground smooth on several 

 sides, and thus facetted, so as to resemble human flint implements. Shaler 

 mentions the frequent occurrence of such facetted stones on Kantucket, and 

 W. P. Blake has found many over Mill Rock, near New Haven, Conn. 



The process of decomposition went forward rapidly because the stones 

 were in a moist place, and the needed air penetrated all glaciers. Moreover, / 

 through the c arbonic aci d__p resent in the_J£e,_.as it is present in all rain or ' 

 snow, decomposition of other kinds went forward, and especially that of 

 changing the finely powdered feldspar to clay (page 129). The microscopic 

 vegetation not uncommon in glacier ice, including that of Greenland, may, 

 through its decay, have afforded additional carbonic acid, and also organic 

 acids for the work of decomposition. 



There is little of this clay made in the region of the Alps, but it was 

 almost universal when the continental ice flowed over regions Avhere crystal- 

 line rocks were to be had ; and the distribution of clay in great beds over 

 glaciated areas, as well as in the bowlder clay, is thus accounted for. 



The invading ice in its first movement trod down the forests and carried 

 off the broken trunks ; and some trunks and stumps and eddy-like gatherings 

 of leaves in the till or bowlder clay of Ohio, Indiana, Illinois, and other 

 states west may have thus been gathered. The accumulation of soil and the 

 growth of forests over the debris that accumulates on the melting margin of 

 a glacier, as on the St. Elias glacier (page 239), illustrates a common process 

 of the Ice age. 



2. Transportation. — In the Avork of transportation both ice and water 

 were concerned. Melting, through the warmer season, and copious rains sup- 

 plied the water. The glaciers of the Alps and Greenland teach that super- 

 glacial lakes and streams may thus have been made, which contributed water 

 to sub-glacial rivers. 



The distance of transportation by the glacier varied from 10 miles or less 

 to 500 ; and more examples of distant travel would exist if stones did not 

 wear out. Native copper has the advantage of stone, and some of its masses 

 made a journey of at least 450 miles, as stated on page 952. 



The direction of travel is sometimes indicated by the occurrence of long 

 trains of stones leading off from the ledge or peak which afforded them. A 

 hill of hard quartzose chloritic rocks on the borders of Lebanon and Canaan, 

 in Rensselaer County, IS". Y., was the parent source of the •' Richmond " train 

 of large stones that crosses the Taconic Range into Massachusetts, and is 

 continued on over Richmond and Lenox into Tyringham (S. Reid, 1842, E. 

 Hitchcock, 1844, E. R. Benton, 1878). 



Some of the transported bowlders exceed 1000 tons in weight. The 

 "Churchill Rock" at Nottingham, N.H., described by C. H. Hitchcock, is 62, 

 40, and 40 feet in its diameters, and is estimated to weigh about 6000 tons. 



