In "A Visit from St. Nicholas," what does the simile in lines 25-27 compare?

Let us remember that a simile is an example of figurative
language that compares one object with another that we normally would not associate it with using
the words "like" or "as." Let us examine the simile you have identified to discover what two
things it is comparing:

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As dry leaves that before the wild hurricane
fly,

When they meet with an obstacle, mount to the
sky.

So up to the house-top the coursers they
flew,

With a sleigh full of Toys, and St. Nicholas
too.

Notice how the first two lines
establish the comparison, with the word "As." Dry leaves that suddenly surge up into the air when
they meet an obstacle in their path are thus one of the elements of this simile. The second
element can be found in the last two lines of this stanza, and we can see that the course of the
dry leaves and the way they suddenly surge up is compared to "the coursers" (the reindeer) and
the way in which they suddenly went up to the top of the house.