We can perhaps best 
appreciate the process 
by which these lakes 
are made by returning 
in our minds to the 
conditions that must 
have prevailed about 
| the end of the period 
during which these 
sediments were depos- 
ited. The beds were 
then at or below sea- 
level; subsequently 
they were lifted verti- 
cally from beneath the 
water and stream ero- 
sion began to cut val- 
leys in them, while 
the waves of the sea 
attacked their margins. 
In the course of time 
broad valleys were |, 
eroded out where we 
| 
From a photograph taken from Fernäo Velho. 
now have Тарба do $ 
| Norte, Lagóa Mangu- E 
| aba, Jiquiä, etc. After p" 
the cutting of these B 
valleys there came a | ji E 
downward movement " A 
| which carried the bot- a S 
toms of all of them u $ 
below the level of the i " H 
sea, and made bays of i 5 
them, But inasmuch | 5 
| Е 
as land erosion con- | 
tinued over the part | 
still out of water the 1 
streams carried their | 1 
sediments into these ; 4 
bays and began to silt | 1 | 
them up. The sea also, ' L4 
cutting sands from the | | E 
headlands, threw them 1 | 3. 
| 
| 
i 
