Here was indeed a
      mystery which I felt it impossible to explain; but, even at that
      early moment, there seemed to glimmer, faintly, within the most
      remote and secret chambers of my intellect, a glow-worm-like
      conception of that truth which last night’s adventure brought to
      so magnificent a demonstration. I arose at once, and putting the
      parchment securely away, dismissed all farther reflection until I
      should be alone. “When you had gone, and when Jupiter was fast asleep, I betook
      myself to a more methodical investigation of the affair. In the
      first place I considered the manner in which the parchment had
      come into my possession. The spot where we discovered the
      _scarabæus_ was on the coast of the main land, about a mile
      eastward of the island, and but a short distance above high water
      mark. Upon my taking hold of it, it gave me a sharp bite, which
      caused me to let it drop. Jupiter, with his accustomed caution,
      before seizing the insect, which had flown towards him, looked
      about him for a leaf, or something of that nature, by which to
      take hold of it. It was at this moment that his eyes, and mine
      also, fell upon the scrap of parchment, which I then supposed to
      be paper. It was lying half buried in the sand, a corner sticking
      up. Near the spot where we found it, I observed the remnants of
      the hull of what appeared to have been a ship’s long boat. The
      wreck seemed to have been there for a very great while; for the
      resemblance to boat timbers could scarcely be traced. “Well, Jupiter picked up the parchment, wrapped the beetle in it,
      and gave it to me. Soon afterwards we turned to go home, and on
      the way met Lieutenant G——. I showed him the insect, and he
      begged me to let him take it to the fort. Upon my consenting, he
      thrust it forthwith into his waistcoat pocket, without the
      parchment in which it had been wrapped, and which I had continued
      to hold in my hand during his inspection. Perhaps he dreaded my
      changing my mind, and thought it best to make sure of the prize
      at once—you know how enthusiastic he is on all subjects connected
      with Natural History. At the same time, without being conscious
      of it, I must have deposited the parchment in my own pocket. “You remember that when I went to the table, for the purpose of
      making a sketch of the beetle, I found no paper where it was
      usually kept. I looked in the drawer, and found none there. I
      searched my pockets, hoping to find an old letter, when my hand
      fell upon the parchment. I thus detail the precise mode in which
      it came into my possession; for the circumstances impressed me
      with peculiar force. “No doubt you will think me fanciful—but I had already
      established a kind of connexion. I had put together two links of
      a great chain. There was a boat lying upon a sea-coast, and not
      far from the boat was a parchment—not a paper—with a skull
      depicted upon it. You will, of course, ask ‘where is the
      connexion?’ I reply that the skull, or death’s-head, is the
      well-known emblem of the pirate. The flag of the death’s head is
      hoisted in all engagements. “I have said that the scrap was parchment, and not paper. Parchment is durable—almost imperishable. Matters of little
      moment are rarely consigned to parchment; since, for the mere
      ordinary purposes of drawing or writing, it is not nearly so well
      adapted as paper. This reflection suggested some meaning—some
      relevancy—in the death’s-head. I did not fail to observe, also,
      the form of the parchment. Although one of its corners had been,
      by some accident, destroyed, it could be seen that the original
      form was oblong. It was just such a slip, indeed, as might have
      been chosen for a memorandum—for a record of something to be long
      remembered and carefully preserved.”

      “But,” I interposed, “you say that the skull was not upon the
      parchment when you made the drawing of the beetle. How then do
      you trace any connexion between the boat and the skull—since this
      latter, according to your own admission, must have been designed
      (God only knows how or by whom) at some period subsequent to your
      sketching the _scarabæus?_”

      “Ah, hereupon turns the whole mystery; although the secret, at
      this point, I had comparatively little difficulty in solving. My
      steps were sure, and could afford but a single result. I
      reasoned, for example, thus: When I drew the _scarabæus_, there
      was no skull apparent upon the parchment. When I had completed
      the drawing I gave it to you, and observed you narrowly until you
      returned it. You, therefore, did not design the skull, and no one
      else was present to do it. Then it was not done by human agency. And nevertheless it was done. “At this stage of my reflections I endeavored to remember, and
      did remember, with entire distinctness, every incident which
      occurred about the period in question. The weather was chilly (oh
      rare and happy accident! ), and a fire was blazing upon the
      hearth. I was heated with exercise and sat near the table. You,
      however, had drawn a chair close to the chimney. Just as I placed
      the parchment in your hand, and as you were in the act of
      inspecting it, Wolf, the Newfoundland, entered, and leaped upon
      your shoulders. With your left hand you caressed him and kept him
      off, while your right, holding the parchment, was permitted to
      fall listlessly between your knees, and in close proximity to the
      fire. At one moment I thought the blaze had caught it, and was
      about to caution you, but, before I could speak, you had
      withdrawn it, and were engaged in its examination. When I
      considered all these particulars, I doubted not for a moment that
      heat had been the agent in bringing to light, upon the parchment,
      the skull which I saw designed upon it. You are well aware that
      chemical preparations exist, and have existed time out of mind,
      by means of which it is possible to write upon either paper or
      vellum, so that the characters shall become visible only when
      subjected to the action of fire. Zaffre, digested in aqua regia,
      and diluted with four times its weight of water, is sometimes
      employed; a green tint results. The regulus of cobalt, dissolved
      in spirit of nitre, gives a red. These colors disappear at longer
      or shorter intervals after the material written upon cools, but
      again become apparent upon the re-application of heat. “I now scrutinized the death’s-head with care. Its outer
      edges—the edges of the drawing nearest the edge of the
      vellum—were far more distinct than the others.