VALLEY OF THE AMAZONS. 
205 
a fresh-water basin ; these deposits are fresh¬ 
water deposits. But as the Yalley of the Am¬ 
azons exists to-day, it is widely open to the 
ocean on the east, with a gentle slope from the 
Andes to the Atlantic, determining a powerful 
seaward current. When these vast accumu¬ 
lations took place, the basin must have been 
closed; otherwise the loose materials would con¬ 
stantly have been carried down to the ocean. 
It is my belief that all these deposits belong 
to the ice-period in its earlier or later phases; 
and to this cosmic winter, which, judging from 
all the phenomena connected with it, may have 
lasted for thousands of centuries, we must look 
for the key to the geological history of the 
Amazonian Yalley. I am aware that this 
suggestion will appear extravagant. But is 
it, after all, so improbable that, when Central 
Europe was covered with ice thousands of 
feet thick ; when the glaciers of Great Britain 
ploughed into the sea, and when those of the 
Swiss mountains had ten times their present 
altitude; when every lake in Northern Italy 
was filled with ice, and these frozen masses 
extended even into Northern Africa; when a 
sheet of ice, reaching nearly to the summit of 
