50.  REFLEX=_reflection_. Cf.: 

Like the reflex of the moon
Seen in a wave under green leaves. 
Shelley, Prometheus Unbound, iii, 4.

In later editions Wordsworth altered these lines as follows: 

To cut across the image. 1809.  To cross the bright reflection. 1820.

54-60.  The effect of rapid motion is admirably described.  The spinning effect which Wordsworth evidently has in mind we have all noticed in the fields which seem to revolve when viewed from a swiftly moving:  train.  However, a skater from the low level of a stream would see only the fringe of trees sweep past him.  The darkness and the height of the banks would not permit him to see the relatively motionless objects in the distance in either hand.

57-58.  This method of stopping short upon one’s heels might prove disastrous.

58-60.  The effect of motion persists after the motion has ceased.

62 63.  The apparent motion of the cliffs grows feebler by degrees until “all was tranquil as a summer sea.”  In The [Transcriber’s note:  the rest of this footnote is missing from the original book because of a printing error.]

TO THE REV.  DR. WORDSWORTH

  (WITH THE SONNETS TO THE RIVER DUDDON, AND OTHER
  POEMS IN THIS COLLECTION, 1820).

  The minstrels played their Christmas tune
  To-night beneath my cottage-eaves;
  While, smitten by a lofty moon,
  The encircling laurels, thick with leaves,
  Gave back a rich and dazzling sheen, 5
  That overpowered their natural green.

  Through hill and valley every breeze
  Had sunk to rest with folded wings;
  Keen was the air, but could not freeze,
  Nor check, the music of the strings; 10
  So stout and hardy were the band
  That scraped the chords with strenuous hand: 

  And who but listened?—­till was paid
  Respect to every Inmate’s claim: 
  The greeting given, the music played, 15
  In honor of each household name,
  Duly pronounced with lusty call,
  And “Merry Christmas” wished to all!

  O Brother!  I revere the choice
  That took thee from thy native hills; 20
  And it is given thee to rejoice: 
  Though public care full often tills
  (Heaven only witness of the toil)
  A barren and ungrateful soil.

  Yet, would that Thou, with me and mine, 25
  Hadst heard this never-failing rite;
  And seen on other faces shine
  A true revival of the light
  Which Nature and these rustic Powers,
  In simple childhood, spread through ours! 30

  For pleasure hath not ceased to wait
  On these expected annual rounds;
  Whether the rich man’s sumptuous gate
  Call forth the unelaborate sounds,
  Or they are offered at the door 35
  That guards the lowliest of the poor.