Darwin, who in his work on 'The Expression of the Emotions in Man and Animals' (London, 1872; p. 87) mentions the astonishing musical skill of this ape, remarks that some quadrupeds of a much lower class than monkeys, namely Rodents, "are able to produce correct musical tones," and he refers the reader to an account of a "singing Hesperomys" [a mouse] by the Rev. S. Lockwood, in the 'American Naturalist,' Vol. V., December, 1871; p. 761. Notwithstanding the great authority of Darwin, the musical inquirer will probably desire to ascertain for himself whether the "correct musical tones" are exactly in conformity with our diatonic and chromatic intervals. However, even if this should be the case in a few instances, it can only be regarded as quite exceptional. During the present century, our musical composers have so frequently employed in the diatonic major scale the Minor Sixth instead of the Major Sixth, that some theorists--among them Moritz Hauptmann--notice this order of intervals as a new and characteristic scale, and desire to have it as such generally acknowledged by musicians. A. Krauss, a teacher of music in Florence, has recently published a pamphlet, entitled 'Les Quatre Gammes diatoniques de la Tonalite moderne,' in which he designates this new scale with the name 'La Gamme semimajeur' (The Half-major Scale,) which is at any rate better than that suggested by Moritz Hauptmann, in his 'Die Natur der Harmonik and der Metrik,' which is 'Die Moll-Dur-Tonart' (the Minor-Major-Key, or scale). We possess then, according to these theorists, now four diatonic scales, namely:-- [Music: 1. THE MAJOR SCALE.] [Music: 2. THE HALF-MAJOR SCALE.] Or also with minor seventh in descending: [Music: 3. THE MINOR SCALE.] [Music: 4. THE HALF-MINOR SCALE.] The Half-Minor Scale contains the Minor Third, while its other intervals are identical with those of the Major Scale. This is the case in descending, where the seventh and sixth are lowered, as well as in ascending. Furthermore, we have the Chromatic Scale, a regular progression in semitones, which is much used by modern composers; and the Enharmonic Scale, which may be said to exist only in notation, since it is not executable on most of our musical instruments, but which is likely to become important in the music of a future period when our instruments have been brought to the degree of perfection which permits the most delicate modifications in pitch by the performer, and which is at present almost alone obtainable on instruments of the violin kind. [Music: 5. THE CHROMATIC SCALE.] [Music: 6. THE ENHARMONIC SCALE.] Furthermore, we find at the present day the following scales in use among foreign nations:-- [Music: 7. THE MINOR SCALE WITH TWO SUPERFLUOUS SECONDS.]