i8o 
K. F. Mather 
valleys are only found in a few localities and are not a general i 
feature of the terrace structure. As a rule the terraces are made | 
up of stratified and cross-bedded gravels, clays, and sands, alter- j 
nating locally with areas of unstratified gravels. They present all 
the appearance of fluvio-glacial deposits made in a ponded or very 
sluggish stream containing unstable currents overloaded with 
material from the melting ice. This same conclusion is reached in 
a consideration of a similar deposit at Andover, Mass.^ A photo- 
graph of the delta-plain material at that place presents an appear- j 
ance very similar to that described in these terraces. I! 
The terrace in valley A extends across the divide through the j 
channel K into valley B. Here the same persistent terrace is I 
found at a corresponding level. It sustains a similar relation to | 
the brook as does the terrace in the first valley except that here j 
there has been a little more erosion since its formation. This, | 
however, is not antagonistic to the idea that the two terraces were ; 
formed at the same time in the same body of water because trib- 
utary A has been held up by a rock barrier near its confluence 
with the Licking while stream B everj/where flows on a till floor. 
In valley C the same sort of a terrace, composed of similar mate- 
rials, is found on both sides of the valley. At first inspection it 
appeared to he about the same elevation as the terraces in the other 
two valleys but when the topographical map of the region was 
obtained it became evident that here there w^as a discrepancy. 
The elevation of the terraces in valleys A and B is 830 feet while 
that in valley C is only 810 feet above sea level. The necessity j 
of attributing these terraces to lacustrine deposition is here accen- j 
tuated by the fact that at the southern end of the valley, where two i 
smaller streams converge to form the tributary L, there are found | 
delta-like deposits at the mouths of each of the small brooks. 
These delta-fans are the result of deposition, at the time that the 
lake occupied the valley, of the material brought to the lake by 
these two small streams. I 
It was pointed out that these terraces all contained assorted | 
glacial drift, but in valley D no terrace nor glacial drift was dis- 
covered. This last valley, although younger and smaller than any 
of the three others, is of pre-glacial age. It is, also, broad enough 
to favor the formation and preservation of this same sort of ter- 
race if glacial waters had been ponded in it. 
F. S. Mills: American Geologist, vol. xxxii, pp. 162-170, 1903. 
