Cryptogram from Frankenstein; or, the modern prometheus, chapter 24

I cannot guess how many days have passed since then, but I have endured misery which nothing but the eternal sentiment of a just retribution burning within my heart could have enabled me to support. Immense and rugged mountains of ice often barred up my passage, and I often heard the thunder of the ground sea, which threatened my destruction. But again the frost came and made the paths of the sea secure.

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But this was not the time for delay; I disencumbered the dogs of their dead companion, gave them a plentiful portion of food, and after an hour's rest, which was absolutely necessary, and yet which was bitterly irksome to me, I continued my route. The sledge was still visible, nor did I again lose sight of it except at the moments when for a short time some ice-rock concealed it with its intervening crags. I indeed perceptibly gained on it, and when, after nearly two days' journey, I beheld my enemy at no more than a mile distant, my heart bounded within me.