Cryptogram from Frankenstein; or, the modern prometheus, chapter 22

Elizabeth seemed happy; my tranquil demeanour contributed greatly to calm her mind. But on the day that was to fulfil my wishes and my destiny, she was melancholy, and a presentiment of evil pervaded her; and perhaps also she thought of the dreadful secret which I had promised to reveal to her on the following day. My father was in the meantime overjoyed, and, in the bustle of preparation, only recognised in the melancholy of his niece the diffidence of a bride.

The sentence you are solving goes here.

Those were the last moments of my life during which I enjoyed the feeling of happiness. We passed rapidly along; the sun was hot, but we were sheltered from its rays by a kind of canopy while we enjoyed the beauty of the scene, sometimes on one side of the lake, where we saw Mont Salêve, the pleasant banks of Montalègre, and at a distance, surmounting all, the beautiful Mont Blanc, and the assemblage of snowy mountains that in vain endeavour to emulate her; sometimes coasting the opposite banks, we saw the mighty Jura opposing its dark side to the ambition that would quit its native country, and an almost insurmountable barrier to the invader who should wish to enslave it.