This is the section of the poem to which you are referring:

..the fiery band which held
Their natures, snaps--while the shock still may tingle
One falls and then another in the path
Senseless--nor is the desolation single, _160

Yet ere I can say WHERE--the chariot hath
Passed over them--nor other trace I find
But as of foam after the ocean's wrath

Is spent upon the desert shore;--behind,
Old men and women foully disarrayed, _165
Shake their gray hairs in the insulting wind,

And follow in the dance, with limbs decayed,
Seeking to reach the light which leaves them still
Farther behind and deeper in the shade.

But not the less with impotence of will _170
They wheel, though ghastly shadows interpose
Round them and round each other, and fulfil

Their work, and in the dust from whence they rose
Sink, and corruption veils them as they lie,
And past in these performs what,...

Generally, lines of poetry can be discussed as a separate entity and as a part of the greater whole.  It is generally best to do both.

These lines discuss the decay and degeneration of the people whom the Chariot of Life has both run over and enslaved.  These people are described as being broken and demoralized but have no choice but to slavishly continue to follow the Chariot. 

These lines may be confusing by themselves, but in the greater context of the poem, the reader can see that these people are those that have given in to the worldy temptations of Life, which is personified as the Shape and its Chariot.  Metaphorically, Life has "run over" them, leaving them in God's anger and without salvation, which is most apparent in lines 168-169.

The words you mention are, indeed, misspelled.  They  are "natures," "deserts," and "foully,"  from lines 2,7, and 8 respectively. 

You specifically ask about similes.  In the lines directly preceeding this selection, lines 152-155, similes are used.

...and as they glow,
Like moths by light attracted and repelled,
Oft to their bright destruction come and go,

Till like two clouds into one vale impelled, _155
That shake the mountains when their lightnings mingle And die in rain..

This passage refers to young people who, during their youth, are attracted like insects to light, or to bright but senseless things such as wealth.  Then they seem to dart back and forth.  He uses another simile for the destruction they turn into by comparing them to two clouds which cause a violent and fatal storm.