TARR AND WOODWORTH: CHANGES OF LEVEL AT CAPE ANN. 185 
A deposit apparently of the same origin occurs near the mouth of the 
Alewife brook (K, Plate 1), the outlet of Cape Pond. It is now so 
badly destroyed by excavations for street grading that the form is not 
preserved ; but before these excavations were made the features of the 
delta were plainly seen. One feature in connection with this deposit is 
the presence of abundant boulders of large size, showing that while the 
water was depositing the layers there was some means —as floating ice 
—for the transportation of large rock masses. The Alewife brook 
delta deposit extends up stream for a long distance, the valley being 
bordered, sometimes on both sides, but more often on only one, by 
stratified, terrace-like beds. One of these is locally known as the “Sand 
Pit,” and even farther upstream than this, at about the level of the 
former coast line, is an extensive stretch of level land now for the most 
part occupied by aswamp. The association of these features with the 
largest brook on the Cape leads to the belief, when taken in connection 
with the other evidence, that this is really a delta formed in the sea 
during a lower stand of the land, 
At that part of the delta first described, the Alewife brook turns 
abruptly at right angles to the north and changes its character from a 
brook to a tidal stream called Mill “River.” A large part of Mill 
“ River” valley bottom is salt marsh; but this is flanked on either side 
by stratified beds which extend from Riverdale into the city of Glouces- 
ter (I J, Plate 1). So much building has been done over a large part of 
this level, stratified area that one cannot now tell what its original condi- 
tion was; but in that region, wherever cuts have been made at levels 
below the 45 foot contour line, they have revealed stratified drift. This 
region is so enclosed by hills that it is impossible to consider these de- 
posits as beaches, but their uniformity of extent at the former sea level 
leads to the belief that they are connected in origin with the former sea 
level. There is now no stream which could have formed such extensive 
beds of stratified deposit, but it is noteworthy that they are located along 
the broad north-south depression which, at the present stand of the sea, 
completely cuts the end of Cape Ann from the mainland, transforming it 
to an island. While the ice front was building the Cape Ann moraine, 
water from the melting glacier was doubtless supplied to this valley ; 
and it is also possible that it served as the outlet for a subglacial stream, 
which would account for the stratified deposits that abound along the 
valley sides and bottom. 
This explanation, which seems the only possible one, would assign to 
the stratified beds in the neighborhood of the city of Gloucester an origin 
