But the music of birds, though agreeable to all, conveys positive and durable pleasure only to those who have learned to associate with their notes, in connection with the scenes of Nature, a thousand interesting and romantic images. To many persons of this character it affords more delight than the most brilliant music of the opera or the concert. In vain, therefore, will it be said, as an objection, that the notes of birds have no charm, save that which is derived from association, and that, considered as music, they do not equal that of the most simple reed or flageolet. It is sufficient to remark, that the most delightful influences of Nature proceed from those sights and sounds that appeal to the imagination and affections through the medium of slight and almost insensible impressions made upon the eye and the ear. At the moment when these physical impressions exceed a certain mean, the spell is broken, and the enjoyment becomes sensual, not intellectual. How soon, indeed, would the songs of birds lose their effect, if they were loud and brilliant, like a band of instruments! It is their simplicity that gives them their charm. As a further illustration of this point, it may be remarked that simple melodies have among all people exercised a greater power over the imagination than louder and more complicated music. Nature employs a very small amount of physical sensation to create an intellectual passion, and when an excess is used a diminished effect is produced. I am persuaded that the effect of a great part of our sacred music is lost by an excess of harmony and a too great volume of sound. On the same principle, a loud crash of thunder deafens and terrifies; but its low and distant rumbling produces an agreeable emotion of sublimity.