Many ways of thus tiring the brain have been proposed. The more irksome they are, the more likely they are to prove effectual. Counting a hundred backward many times, listening to monotonous sounds, thinking of some extremely disagreeable and tiresome subject, with many other devices, have been suggested, and have proved more or less effectual. Boerhaave[26] states that he procured sleep by placing a brass pan in such a position that the patient heard the sound of water which was made to fall into it, drop by drop. In general terms, monotony predisposes to sleep. Dr. Dickson[27] quotes Southey’s experience as related in the Doctor,[28] and I also cannot do better than lay it before the reader, particularly as it indicates several methods which may be more efficacious with others than the one he found to succeed so admirably. “I put my arms out of bed; I turned the pillow for the sake of applying a cold surface to my cheek; I stretched my feet into the cold corner; I listened to the river and to the ticking of my watch; I thought of all sleepy sounds and of all soporific things--the flow of water, the humming of bees, the motion of a boat, the waving of a field of corn, the nodding of a mandarin’s head on the chimney-piece, a horse in a mill, the opera, Mr. Humdrum’s conversations, Mr. Proser’s poems, Mr. Laxative’s speeches, Mr. Lengthy’s sermons. I tried the device of my own childhood, and fancied that the bed rushed with me round and round. At length Morpheus reminded me of Dr. Torpedo’s Divinity Lectures, where the voice, the manner, the matter, even the very atmosphere and the streamy candlelight were all alike somnific; when he who, by strong effort, lifted up his head and forced open the reluctant eyes never failed to see all around him asleep. Lettuces, cowslip wine, poppy syrup, mandragora, hop pillows, spider’s web pills, and the whole tribe of narcotics, up to bang and the black-drop, would have failed,--but this was irresistible; and thus, twenty years after date, I found benefit from having attended the course.” Frequently the power of the attention is diminished by natural causes. After the mind has been strained a long time in one particular direction, and during which period the brain was doubtless replete with blood, the tension is at last removed, the blood flows out of the brain, the face becomes pale, and sleep ensues. It is thus, as Macnish[29] says, that “the finished gratification of all ardent desires has the effect of inducing slumber; hence after any keen excitement the mind becomes exhausted and speedily relapses into this state.”