Critical Analysis of Letters 1-4

I am reading Frankenstein for an literature class I am currently taking and for this post I am choosing to both summarize letters 1-4 in the beginning of the novel; after readinfg my summary I would like to discuss some of the themes that one may see in the beginning of this novel.

In the beginning of the novel we meet Robert Walton, a sea captain who is on a journey to find a passage from the Pacific to the Atlantic. He writes many letters to his sister in London in named Mrs. Saville. This journey is something that he talked/ dreamed about for many years and now that he gets to do it, he is very happy and since none of his other dreams have manifested themselves he feels as though this must be successful. The writer of the letters is happy that this dream of his will allow for him to satisfy an 'ardent curiosity" since he will be setting foot on another part of the world that someone hasn't been on yet.
To prepare for the trip Walton takes practice trips to Russia and as he takes this practice trip one of the things on his mind is that he doesn't have a friend who will be able to maintain the disappointment that he will feel if the trip doesn't go as he plans.
As it begins, the journey is going well but then in the middle of the ocean they see a sleigh that is being pulled by dogs which then disappears; then the next day there is another sleigh and the person on this sleigh then boards the ship nearly frozen. Walton comes to find out that the person is out looking for someone who ran from him (which happens to be the person from the first sleigh); as Walton spends more time with him he comes to find out how unhappy this person is and that at some point he had the same dreams as Walton but had to abandon them.

For me, I see the development of a heroic theme beginning. Walter is going on an expedition to discover something that is unknown to man to the point he is willing to risk his life just to do this.
What are some other themes that you all see developing in letters 1-4? Let's chat!