"We are going well," said he, looking out the window and glancing at his
watch. "Our rate at present is fifty-three and a half miles an hour."
  "I have not observed the quarter-mile posts," said I.
  "Nor have I. But the telegraph posts upon this line are sixty yards apart,
and the calculation is a simple one."
    -- Sherlock Holmes and Watson, in "Silver Blaze"