The effect of music on the system is explained in two different ways. The monotony of the sound is supposed to have a soothing influence over the mind, similar to what is known to result from the gurgle of a mimic cataract of some mountain rill, or to a distant waterfall. How often has the music caused by the waves gently dashing upon the beach excited sleep, when all our narcotics have failed in producing a similar effect. This soporific effect of the repetition or monotony of sound is beautifully alluded to by Mackenzie, in his Man of Feeling. When his hero, Mr. Harley, arrives in London, he finds that the noise and varied excitement of the metropolis increase his nervous state of habit, and prevent him from sleeping. Ordinary narcotics produce no effect upon him, and he must have continued to suffer from watchfulness if he had not happily touched his shoe-buckle, which lay upon the table, when the vibration produced a monotonous sound so closely resembling the voice of his good aunt, who nightly read him asleep in the country, that from that time he regularly applied to the same narcotic, and always slept soundly. Music acts, secondly, by causing an association of agreeable ideas. A lady who was confined in an asylum in the vicinity of London, and who had been separated for some months from her home, and from all she held dear, was pronounced partially convalescent. She was, however, still melancholy; and it was suggested by her father that a piece, of which she was passionately fond, and which was associated with the happiest period of her life, should be played within her hearing. This wish was complied with; the effect produced was highly gratifying. For the first few minutes, no notice was taken of the music; in a short period, however, a smile was seen to play upon a countenance where all had been dark and gloomy for months. As the music proceeded, the effect became more sensible and powerful; ideas of a most pleasurable kind appeared to rush upon a mind which had previously been a blank; a chord had been touched which thrilled through her, until she appeared absorbed in the pleasing associations which the favourite air had conjured to her recollection. The past was no longer forgotten, and she for the first time gave evidence of being conscious of the situation in which she was in. A fatal blow had been given to the disease, and in a short period she was considered sufficiently recovered to be allowed to return home to the bosom of her family.