of these composers' depth of evocative expression and their marked individuality. In Haydn's music, according to Hoffmann, "a child-like, serene disposition prevails", while Mozart (in the late E-flat major Symphony, for example) "leads us into the depths of the spiritual world", with elements of fear, love, and sorrow, "a presentiment of the infinite ... in the eternal dance of the spheres". Beethoven's music, on the other hand, conveys a sense of "the monstrous and immeasurable", with the pain of an endless longing that "will burst our breasts in a fully coherent concord of all the passions". This elevation in the valuation of pure emotion resulted in the promotion of music from the subordinate position it had held in relation to the verbal and plastic arts during the Enlightenment. Because music was considered to be free of the constraints of reason, imagery, or any other precise concept, it came to be regarded, first in the writings of Wackenroder and Tieck and later by writers such as Schelling and Wagner, as preeminent among the arts, the one best able to express the secrets of the universe, to evoke the spirit world, infinity, and the absolute. This chronologic agreement of musical and literary Romanticism continued as far as the middle of the 19th century, when Richard Wagner denigrated the music of Meyerbeer and Berlioz as "neoromantic": "The Opera, to which we shall now return, has swallowed down the Neoromanticism of Berlioz, too, as a plump, fine-flavoured oyster, whose digestion has conferred on it anew a brisk and well-to-do appearance." It was only toward the end of the 19th century that the newly emergent discipline of Musikwissenschaft (musicology)—itself a product of the historicizing proclivity of the age—attempted a more scientific periodization of music history, and a distinction between Viennese Classical and Romantic periods was proposed. The key figure in this trend was Guido Adler, who viewed Beethoven and Franz Schubert as transitional but essentially Classical composers, with Romanticism achieving full maturity only in the post-Beethoven generation of Frédéric Chopin, Felix Mendelssohn, Robert Schumann, Hector Berlioz and Franz Liszt. From Adler's viewpoint, found in books like Der Stil in der Musik (1911), composers of the New German School and various late-19th-century nationalist composers were not Romantics but "moderns" or "realists" (by analogy with the fields of painting and literature), and this schema remained prevalent through the first decades of the 20th century. By the second