Soon after arriving at Bly, the governess takes stock of her situation, using both a metaphor and a simile to express her feelings about the somewhat ambiguous and daunting circumstances of her employment. First, she metaphorically compares her "circumstances" to something huge, imposing, and intimidating:
They had, as it were, an extent and mass for which I had not been prepared and in the presence of which I found myself, freshly, a little scared as well as a little proud.
By presenting her situation at Bly as such a colossal undertaking, the governess contributes to the ominous and slightly overwhelming quality of her initial days in this new place. And yet, nothing has really happened yet; the governess simply senses the enormity of the task ahead of her, but she has no idea just how intense this experience will truly be—once she starts seeing ghosts, her situation really does become quite daunting.
To that end, the governess uses a simile to further characterize what it feels like to live in the huge mansion at Bly:
[...] I had the fancy of our being almost as lost as a handful of passengers in a great drifting ship. Well, I was, strangely, at the helm!
In this simile, the governess compares her situation at Bly to the experience of being on a large, wayward ship. This is an especially insightful simile because the governess is not only on a ship that seems to be lost—she is lost aboard the ship itself. And yet, she's the one supposedly steering it. This speaks to the deep sense of confusion she experiences when she first arrives at Bly, where she's expected to be more or less in charge and yet doesn't even understand why previous governesses have failed in her position, nor why her employer refuses to correspond with her.
As she tells her story, the governess considers the period just before everything started to go wrong at Bly—that is, the period right before she started seeing the ghosts of Peter Quint and Miss Jessel. She sees this stretch of time as rather idyllic, but she also retrospectively sees it as the calm before the storm, and she uses a metaphor to highlight this feeling:
It may be, of course, above all, that what suddenly broke into this gives the previous time a charm of stillness—that hush in which something gathers or crouches.
The governess metaphorically compares the peacefulness of her initial days at Bly to an ominous kind of "stillness," suggesting that the quiet, idyllic circumstances have taken on a sense of danger in her memory. The impending terror she experiences is presented as a terrible animal about to spring upon her—a metaphor that emphasizes just how overpowering the ghosts are when they do appear, as well as how unprepared the governess is to encounter them.
To really drive this point home, the governess goes on to add a simile, saying, "The change was actually like the spring of a beast." This comparison emphasizes a sense of powerlessness, as if the governess couldn't have possibly done anything to protect herself from the antagonism of the ghosts.