In Chapter 1, when Humphrey is sailing across the San Francisco Bay aboard the Martinez, he muses upon the thick fog blanketing the water. He uses an extended simile to convey his feeling of wonder and romance while looking at the view:
I felt quite amused at [the red-faced man's] unwarranted choler, and while he stumped indignantly up and down, I fell to dwelling upon the romance of the fog. And romantic it certainly was—the fog, like the gray shadow of infinite mystery, brooding over the whirling speck of the earth; and men, mere motes of light and sparkle, cursed with an insane relish for work, riding their steeds of wood and steel through the heart of the mystery, groping their way blindly through the Unseen, and clamoring and clanging in confident speech while their hearts are heavy with incertitude and fear.
Here, Humphrey compares the fog to “the gray shadow of infinite mystery,” suggesting that for him it represents all that lies outside of human perception and understanding—a sense of something bigger than day-to-day existence. He describes people as “mere motes of light and sparkle,” again highlighting how small, insignificant, and short our lives are in the grand scheme of things.
It is also significant to note that at this point in the novel, Humphrey is standing outside of the fog looking in. This represents the way that he is able to exist at a comfortable remove from the hardships of life; rather than participating directly in things, he can look at them from the outside and write about them in a romantic way. When the Martinez sinks, he is abruptly thrown into the fog, which represents the way he is abruptly thrown into adversity and hard work when he is picked up by the Ghost. Although his time aboard the Ghost is difficult, it forces him to participate in life directly rather than merely think and write about it from an outside perspective as he has always done.
The fog could also represent the physical side of life—things like exercise, manual labor, and sexuality, all of which Humphrey experiences for the first time while aboard the Ghost. Before entering the fog, Humphrey is represented as being somewhat unbalanced because he has only experienced the intellectual side of life; but once he emerges on the other side at the end of the novel, he has achieved a balance between the intellectual and the embodied.
In Chapter 2, when Humphrey sees Wolf Larsen for the first time, he uses a simile to compare his physical strength to that of a lion:
[Wolf] was firmly planted on his legs; his feet struck the deck squarely and with surety; every movement of a muscle [...] was decisive, and seemed to come out of a strength that was excessive and overwhelming. In fact, though his strength pervaded every action of his, it seemed but the advertisement of a greater strength that lurked within, that lay dormant and no more than stirred from time to time, but which might arouse, at any moment, terrible and compelling, like the rage of a lion or the wrath of a storm.
Throughout the novel, Wolf is compared to a best of prey—in the above passage he is described as being like a lion, and at other points he is compared to a leopard, an eagle, a tiger, and, of course, a wolf. This repeated comparison of Wolf to predators in nature reflects the way that he uses his physical strength to overpower—and sometimes kill—others. It also reflects his harsh worldview, influenced by the theories of Charles Darwin, that only the fittest survive. He believes that all people are out to get one another deep down, that if anyone else was in his place, they would also use their physical strength to dominate others.
