Rack, n.

Properly, vapor; hence, thin flying broken clouds, or any portion of floating vapor in the sky.

The winds in the upper region, which move the clouds above, which we call the rack.
                                                                                 Bacon.

         The great globe itself,
Yea, all which it inherit, shall dissolve,
And, like this unsubstantial pageant, faded,
Leave not a rack behind.
                                                                                 Shak.

It is disputed however, whether rack in this passage should not be wreck.