During Caesar's civil war he commanded one of Pompey's armies in the Ilerda campaign. He escaped the penalties of being on the losing side in the civil war through two pardons granted by Julius Caesar, before and after the Battle of Pharsalus. Caesar later appointed him to oversee the public library of Rome in 47 BC, but following Caesar's death Mark Antonyproscribed him, resulting in the loss of much of his property, including his library. As the Republic gave way to Empire, Varro gained the favour of Augustus, under whose protection he found the security and quiet to devote himself to study and writing.
In 37 BC, in his old age, he also wrote on agriculture for his wife Fundania, writing a "voluminous" work De re rustica (also called Res rusticae)--similar to Cato the Elder's similar work De agri cultura--on the management of large slave-run estates.
The compilation of the Varronian chronology was an attempt to determine an exact year-by-year timeline of Roman history up to his time. It is based on the traditional sequence of the consuls of the Roman Republic--supplemented, where necessary, by inserting "dictatorial" and "anarchic" years. It has been demonstrated to be somewhat erroneous but has become the widely accepted standard chronology, in large part because it was inscribed on the arch of Augustus in Rome; though that arch no longer stands, a large portion of the chronology has survived under the name of Fasti Capitolini.
His only complete work extant, Rerum rusticarum libri tres (Three Books on Agriculture), has been described as "the well digested system of an experienced and successful farmer who has seen and practised all that he records."
One noteworthy aspect of the work is his anticipation of microbiology and epidemiology. Varro warned his contemporaries to avoid swamps and marshland, since in such areas
there are bred certain minute creatures which cannot be seen by the eyes, but which float in the air and enter the body through the mouth and nose and cause serious diseases.
Plan of the birdhouse at Casinum designed and built by Varro
De lingua latina libri XXV (or On the Latin Language in 25 Books, of which six books (V-X) survive, partly mutilated)
Rerum rusticarum libri III (or Agricultural Topics in Three Books)
Known lost works
Saturarum Menippearum libri CL or Menippean Satires in 150 books
Most of the extant fragments of these works (mostly the grammatical works) can be found in the Goetz-Schoell edition of De Lingua Latina, pp. 199-242; in the collection of Wilmanns, pp. 170-223; and in that of Funaioli, pp. 179-371.
^Several people called Marcellus lived during Varro's time. The identity of this one is unclear.
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