Anxiety: A Baroque Eclogue (published separately in 1947). The first two, with Auden's other new poems from 1940 to 1944, were included in his first collected edition, The Collected Poetry of W. H. Auden (1945), with most of his earlier poems, many in revised versions. 1947–1957 After completing The Age of Anxiety in 1946 he focused again on shorter poems, notably "A Walk After Dark", "The Love Feast", and "The Fall of Rome". Many of these evoked the Italian village where he spent his summers between 1948 and 1957, and his next book, Nones (1951), had a Mediterranean atmosphere new to his work. A new theme was the "sacred importance" of the human body in its ordinary aspect (breathing, sleeping, eating) and the continuity with nature that the body made possible (in contrast to the division between humanity and nature that he had emphasised in the 1930s); his poems on these themes included "In Praise of Limestone" (1948) and "Memorial for the City" (1949). In 1949, Auden and Kallman wrote the libretto for Igor Stravinsky's opera The Rake's Progress, and later collaborated on two libretti for operas by Hans Werner Henze. Auden's first separate prose book was The Enchafèd Flood: The Romantic Iconography of the Sea (1950), based on a series of lectures on the image of the sea in romantic literature. Between 1949 and 1954 he worked on a sequence of seven Good Friday poems, titled "Horae Canonicae", an encyclopaedic survey of geological, biological, cultural, and personal history, focused on the irreversible act of murder; the poem was also a study in cyclical and linear ideas of time. While writing this, he also wrote "Bucolics," a sequence of seven poems about man's relation to nature. Both sequences appeared in his next book, The Shield of Achilles (1955), with other short poems, including the book's title poem, "Fleet Visit", and "Epitaph for the Unknown Soldier". In 1955–56 Auden wrote a group of poems about "history", the term he used to mean the set of unique events made by human choices, as opposed to "nature", the set of involuntary events created by natural processes, statistics, and anonymous forces such as crowds. These poems included "T the Great", "The Maker", and the title poem of his next collection Homage to Clio (1960). Later work, 1958–1973 In the late 1950s Auden's style became less rhetorical while its range of styles increased. In 1958,