I think the answer is "and"
what type of essay is it ?
Muir's use of diction in this paragraph, clearly shows how effective his language. The bolded words, like difficult, force, crooked, struggling, etc. create a tense, painful, and frustrating mood. Muir uses these words describe how his journey was through the wading bogs, and swamps and he uses these words to describe what he went through before finding the Calypso Borealis.