Does Walton ever actually find a northern trade route to the Americas in Frankenstein?
In short, no. He sets out to find one and spends many years at sea, and is prepared to spend many more, however, due to his encounter with Victor Frankenstein, he changes his mind and goes back to England. He realizes that his pursuit for this passage is not unlike the pursuit of knowledge that Victor was seeking. It is driven by a blind ambition that risks too much. Just as Victor lost many of his loved ones, and his sanity, in pursuit of his dream, Walton recognizes that he acting with the same tunnel-vision that propelled Victor.
"Yet, it is terrible to reflect that the lives of all these men are endangered through me. If we are lost, my mad schemes are the cause" (Ch. XXIV).
He ends up turning back to go home before he finds the passage.
"The die is cast;I have consented to return, if we are not destroyed. Thus are my hopes blasted to cowardice and indecision; I come back ignorant and disappointed" (Ch. XXIV).
While unhappy at returning before accomplishing his task of finding a passage, he avoids making some of the same mistakes that Victor made.