GEOLOGY. 



RIVER TERRACES OF THE CONNECTICUT VALLEY. 



229 



AT the late meeting of the American Association, President Hitch- 

 cock, of Amherst College, read an interesting paper ; ' On .the River Ter- 

 races of the Connecticut Valley." He stated that his paper must be 

 considered as containing a few facts and suggestions, and not a finished 

 theory. He had examined the valley from its mouth to Turner's Falls, 

 and carefully measured the heights of the terraces. " As you approach 

 the river, you find plains of sand, gravel, or loam, terminated by a slope, 

 sometimes as steep as 35, and a second plain, then another slope and 

 another plain, and so on, sometimes to a great number. I find that 

 these terraces occur in successive basins, formed by the approaches of 

 the mountains upon the banks, at intervals. Sometimes the basin 

 will be 15 or 20 miles in width, but usually much narrower; and it 

 is upon the margins of these basins that the terraces are formed. I 

 have rarely found terraces more than 200 feet above the river ; which 

 would be, in Massachusetts, about 300 feet above the ocean, and at 

 Hanover, N. H., about 560 feet. Nowhere do they exist along any 

 river, unless that river has basins. As to the materials of which they 

 are formed, they appear exceedingly artificial. The outer or highest 

 terrace is generally composed of coarser materials than the inner ones. 

 All are formed of materials which are worn from the rocks, but the 

 outer terrace oftener is full of pebbles, some of them as large as 

 12 inches, while the materials of the inner seem reduced to an 

 impalpable powder, like the soil of a meadow which is overflowed 

 during high water. Whence did these materials originate ? They 

 were first worn from solid rocks, and afterwards brought into these 

 valleys. The outer terrace appears to have been often in part the 

 result of the drift agency. Afterwards the river agency sorted the ma- 

 terials, and gave them a level surface, the successive basins having at 

 that time barriers. The inner terrace appears to have been, at least in 

 its upper part, the result of deposition from the river itself. 



" I will now mention a few facts which I have observed. The ter- 

 races do not generally agree in height upon the opposite sides of the 

 valley. The higher ones oftener agree, perhaps, than the lower ones. 

 If formed, as I suppose, from the rivers, we should expect this. The 

 terraces slope downward in the direction of the stream. The same 

 terrace which, near Soutli Hadley, is 190 feet above the river, 

 slopes until, at East Hartford, it is only 40 feet above the river, thus 

 sloping 150 feet more than the slope of the river itself, in a distance 

 of 40 or 50 miles. This shows that they could not have been formed 

 by the sea or by a lake, for they would then have been horizontal. 

 The greatest number of terraces observed is eight or nine ; generally, 

 there are but two or three." President H. enters much into detail, 

 stating his theory of the formation of these terraces, with many facts in 

 support of it, We have confined ourselves to his principal statements, 

 as no abstract could give a correct idea of his views ; and they are too 

 long for insertion entire. 



20 



