A Marvel

An old astronomer there was
  Who lived up in a tower,
Named Ptolemy Copernicus
  Flammarion McGower.
He said: "I can prognosticate
  With estimates correct;
And when the skies I contemplate,
  I know what to expect.
When dark'ning clouds obscure my sight,
  I think perhaps 'twill rain;
And when the stars are shining bright,
  I know 'tis clear again."
And then abstractedly he scanned
  The heavens, hour by hour,
Old Ptolemy Copernicus
  Flammarion McGower.