Sentence:  At last I came to the great barrier-cliffs; and after three days of mad effort--of maniacal effort--I <WSD>scaled</WSD> them. I built crude ladders; I wedged sticks in narrow fissures; I chopped toe-holds and finger-holds with my long knife; but at last I <WSD>scaled</WSD> them. Near the summit I came upon a huge cavern. 
Meaning of the word marked with <WSD> tags:  To climb to the top of.