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7 And God made the firmament, and divided the waters which were under the firmament from the waters which were above the firmament: and it was so.
'A sandal tree' signifies aspects of the natural self.
(References: Apocalypse Explained 518)
8 Egypt rises up like the Nile, and his waters toss themselves like the rivers: and he says, I will rise up, I will cover the earth; I will destroy cities and its inhabitants.