during the melting of the Glacier. 429 
4. THE RIVER THAMES. 
The conditions of the stratified drift deposits of Norwich are 
similar in several respects to those about Birmingham. Two 
rivers from the northward, the Quinebaug and the Yantic, pass 
either side of the city and unite below it to make the Thames. 
They rise in Massachusetts, and have nearly the same drainage- 
area as the two that join at Birmingham. They descend from 
high land and most of the way in rapids. Immediately below 
Norwich the valley is so narrowed by hills over 150 feet high 
that the width of the river, were the water 100 feet above 
its present level, would be hardly halfa mile. But below these 
Narrows the valley expands, though still closely bounded 
by high land. The points in which the two cases differ are 
these : 
(1.) The Narrows have greater width, and the modern 
stream below has much greater depth as well as breadth: the 
channel being one of the tidal, navigable fiords of the coast, the 
tides at Norwich having a range of more than three feet. Con- 
sequently it offered the flood-waters a less contracted way to 
(2.) The distance from the Narrows to the Sound is greater, 
being 144 miles, 
(3.) Although this distance is so much greater, the highest 
spring floods cause a rise above high tide of but 74 feet—much 
less than half that in the Housatonic at Birmingham. 
Again, (4,) the terrace plain of upper Norwich—the site of 
Broadway and its many fine residences—has over its northern 
part (at the foot of the little triangular Green) a height above 
tide level of 117 feet ;* and, since the spring floods raise the 
water but 74 feet above high tide, about 110 feet above 
ood level, against 95 feet at Birmingham. a 
The height of the Norwich plain above flood level diminishes 
from 110 in its northern part to 101 feet in its southern, a dis- 
tance of about a mile; and this is very nearly the level of the 
terrace to the eastward of the latter at the Old Cemetery. 
tetery, for example,—are mai 
gravel, the waters were the hurrying waters of a great torrent. 
That this was the actual condition is proved further by the 
heights and nature of the terraces below Norwich. For they 
ue. hare these numbers from the Water Commissioner of the city of Norwich, 
the wy inship. I have been much aided in the study of this region by a map of 
a. giving contour lines for 50, 100 and 200 feet, which was furnished 
by the Superintendent of the Coast Survey. 
