The Georgics is the second major work by the Latin poet Virgil. It is a poem that draws on many prior sources and influenced many later authors from antiquity to the present. As the name suggests, the subject of the poem is agriculture; but far from being an example of peaceful rural poetry, it is a work characterized by tensions in both theme and purpose. The work consists of 2,188 hexametric verses divided into four books. The yearly timings by the rising and setting of particular stars were valid for the precession epoch of Virgil's time, and so are not always valid now. Book One: Virgil begins his poem with a summary of the four books, followed by a prayer to various agricultural deities as well as Augustus himself. It takes as its model the work on farming by Varro, but differs from it in important ways. Numerous technical passages fill out the first half of Book 1. Book Two: Prominent themes of the second book include agriculture as man's struggle against a hostile natural world, often described in violent terms, and the ages of Saturn and Jupiter. Like the first book, it begins with a poem addressing the divinities associated with the matters about to be discussed: viticulture, trees, and the olive. In the next hundred lines Virgil treats forest and fruit trees. Their propagation and growth are described in detail, with a contrast drawn between methods that are natural and those that require human intervention. Three sections on grafting are of particular interest: presented as marvels of man's alteration of nature, many of the examples Virgil gives are unlikely or impossible. Also included is a catalogue of the world's trees, set forth in rapid succession, and other products of various lands. Book Three: The third book is chiefly and ostensibly concerned with animal husbandry. It consists of two principal parts, the first half is devoted to the selection of breed stock and the breeding of horses and cattle. It concludes with a description of the furor induced in all animals by sexual desire. The second half of the book is devoted to the care and protection of sheep and goats and their byproducts. It concludes with a description of the havoc and devastation caused by a plague in Noricum. Both halves begin with a short prologue called a proem. The poems invoke Greek and Italian gods and address such issues as Virgil's intention to honor both Caesar and his patron Maecenas, as well as his lofty poetic aspirations and the difficulty of the material to follow. Many have observed the parallels between the dramatic endings of each half of this book and the irresistible power of their respective themes of love and death. Book Four: Book four, a tonal counterpart to Book two, is divided approximately in half; the first half is didactic and deals with the life and habits of bees, supposedly a model for human society. Bees resemble man in that they labor, are devoted to a king and give their lives for the sake of the community, but they lack the arts and love. In spite of their labor the bees perish and the entire colony dies.