Notices of Memoirs — The Glacial Era in Neic England. 277 



and excursions over the country with accompanying sections and a 

 new geological map, the basis of wiiich is entirely new and com- 

 piled by him from the surveys of Austrian officers, the engineers of 

 the Ottoman railroads, and himself. He also appends a valuable 

 list of heights in the' Eastern portion of European Turkey. 



C. L. Gbiesbach. 



II. — On the Glacial and Champlain Eras in New England. 

 By J. D. Dana.i 



DE. DANA'S observations go to show that the Glacial period was 

 an era of transportation by ice, with th« deposition from the 

 glacier of only a small part of the drift, including the Boulder-clay ; 

 while the early part of the Champlain period, to which he refers the 

 time of melting, was an era eminently of deposition, and also of 

 further transportation by moving waters and floating ice. He re- 

 gards the Glacial period as of great duration, and expi'esses the 

 opinion that one foot a week was the average rate of the movement 

 of the ice, so that 10,000 years would be req[uired to carry a boulder 

 one hundred miles. 



The general course of the movement over New England was to 

 the south-east. In the northern part of this country he estimates 

 the ice to have had a thickness of from 5,000 to 6,500 feet, and in 

 the southern part an average of 2,700 feet. The pressure must 

 have been immense — 6>000 feet corresponding to at least 300,000 

 pounds to the square foot. Under this great pressure there was not 

 only abrasion of the rocks beneath by the ice armed with stones in 

 its lower surface, and also a crushing of softer kinds from mere 

 pressure, but, besides, a breaking and crushing of the ice itself 

 against the obstacles in its course, and also a pressing of the plastic 

 material down among all the stones and gravel or sand ; and thus it 

 was able to envelop and take up into its mass the loose material. 

 Further, the ice of the ice-mass above must have been forced down 

 into all openings and crevices in the rocks, so that the glacier, as it 

 moved, had tremendous power in abrading, and must have made 

 boulders and gravel in immense quantities. 



The valleys of New England have throughout a high terrace along 

 their sides, of material generally stratified, which belongs to the 

 Champlain formation, being merely the old alluvial deposits of this 

 era terraced in consequence of a general rising of the land, when 

 what he has called the Terrace or Kecent epoch began. He is of 

 opinion that in the Quaternarj' period of North America over the 

 higher latitudes, there was an upward movement for the Glacial era, 

 a downward movement below tlie present level for the Champlain 

 era, and an upward one for the Terrace era. 



^ fieprinted from the " American Journal of Science and Arts," vol. v., March, 1873. 



