Both Uses of

external

in

Childhood's End

It was not even certain that they were vertebrates: their hard, external armour might well be their only supporting framework.†
Chpt 7 *

external = outside

And even when the external world has granted all it can, there still remain the searchings of the mind and the longings of the heart.†
Chpt 8

Definition:

outside

in various senses, including:

coming from or existing outside a place, organization or thing -- as in "external trade"
forming or relating to an outside boundary -- as in "external walls"
on the surface or superficial as contrasted to something that is deep or complete -- as in "external appearances"