The panic following a real earthquake, which took place on October 8, 1865, inspired Twain to write this satire:
At the instance of several friends who feel a boding anxiety to know beforehand what sort of phenomena we may expect the elements to exhibit during the next month or two, and who have lost all confidence in the various patent medicine almanacs, because of the unaccountable reticence of those works concerning the extraordinary event of the 8th inst., I have compiled the following almanac expressly for this latitude:

OCT. 17. -- Weather hazy; atmosphere murky and dense. An expression of profound melancholy will be observable upon most countenances.
OCT. 18. -- Slight earthquake. Countenances grow more melancholy.
OCT. 19. -- Look out for rain. It will be absurd to look in for it. The general depression of spirits increased.
OCT. 20. -- More weather.
OCT. 21. -- Same.
OCT 22. -- Light winds, perhaps. If they blow, it will be from the "east'ard, or the nor'ard, or the west'ard, or the suth'ard," or from some general direction approximating more or less to these points of the compass or otherwise. Winds are uncertain--more especially when they blow from whence they cometh and whither they listeth. N.B. -- Such is the nature of winds.
OCT 23. -- Mild, balmy earthquakes.
OCT 24. -- Shaky.
OCT 25. -- Occasional shakes, followed by light showers of bricks and plastering. N.B. -- Stand from under.
OCT 26. -- Considerable phenomenal atmospheric foolishness. About this time expect more earthquakes, but do not look out for them, on account of the bricks.
OCT. 27. -- Universal despondency, indicative of approaching disaster. Abstain from smiling, or indulgence in humorous conversation, or exasperating jokes.
OCT 28. -- Misery, dismal forebodings and despair. Beware of all discourse -- a joke uttered at this time would produce a popular outbreak.
OCT 29. -- Beware!
OCT 30. -- Keep dark!
OCT. 31. -- Go slow!
NOV. 1. -- Terrific earthquake. This is the great earthquake month. More stars fall and more worlds are slathered around carelessly and destroyed in November than in any other month of the twelve.
NOV. 2. -- Spasmodic but exhilerating earthquakes, accompanied by occasional showers of rain, and churches and things.
NOV. 3. -- Make your will.
NOV. 4. -- Sell out.
NOV. 5. -- Select your "last words." Those of John Quincy Adams will do, with the addition of a syllable, thus; "This is the last of earthquakes."
NOV. 6. -- Prepare to shed this mortal coil.
NOV. 7. -- Shed.
NOV. 8 -- The sun will rise as usual, perhaps; but if he does he will doubtless be staggered to find nothing but a large round hole eight thousand miles in diameter in the place where he saw this world serenely spinning the day before.
Illustration: Detail from "Earthquakey Times, San Francisco, Oct. 8, 1865," cartoon by Ed Jump.