“This is the fourth brass cylinder that I have thrown in Lost River in the hope that it will float through the underground passages to the Valley of Arcana, where you may find it. A note accompanied its three predecessors, and each one instructed you to build two signal fires if you found the cylinder so that I would know it had reached you. For several days I have watched the stream of smoke from your fire, longing always to see the second stream ascend. And I have suffered because no second stream came. “I have about decided, therefore, that Lost River does not run through the valley, or that my cylinders have caught on something and failed to reach you. For in some strange way it seems to me that, if they did float into the Valley of Arcana, you would find them. Which is childish of me, I suppose. But it bolsters up my courage nevertheless. I have only three more cylinders to send, and will send them two days apart unless I see the second stream of smoke. “Now follows a repetition of what the other messages contained: “Build another signal fire as soon as you have read this, so that I will know you have received my message and are again in command of the situation. By this time, I think, Andy Jerome will have lapsed into a terrible state, and you will be almost insane. But in the cylinder you will find more tablets. Give him one a day regularly--no more--and if he is not too far gone he will come back to normalcy with surprising swiftness. It may seem incredible to you, but it is the truth. “Andy Jerome, Charmian, is a cretin. A cretin, you perhaps must be told, is an hereditary idiot. Cretinism is most prevalent in the Swiss Alps, where Andy’s ancestors lived--on his mother’s side, I mean. Up until recently cretinism has been considered incurable by the medical profession; but the discovery that man is regulated by his gland secretions had done away with that theory. Cretins are only human beings suffering from a lack of thyroid in their systems. Their other glands may be functioning properly, but when the secretions of the thyroid are deficient they are hopeless idiots. However, science has discovered that if they are fed daily a tablet composed of the extract of the thyroid glands of sheep they will, to all intents and purposes, become normal. But in a few days after the treatment is stopped they will quickly slip back into cretinism again, with all its degradation. Then let the treatment be renewed, and in a short while the patient will have lost all of the symptoms of cretinism and gradually will come back. It seems incomprehensible, I realize, but it is nevertheless a thoroughly demonstrated scientific fact.