Halm is known chiefly as the editor of
Cicero and other
Latin prose authors, although during his early career he also devoted considerable attention to
Greek and also authored an edition of Aesop's fables in the Greek. After the death of
J.C. Orelli, he joined
J.G. Baiter in the preparation of a revised critical edition of the rhetorical and philosophical writings of Cicero (1854–1862). His school editions of some of the speeches of Cicero in the Haupt and Sauppe series, with notes and introductions, were very successful. He also edited a number of classical texts for the
Teubner series, the most important of which are
Tacitus (4th edition, 1883);
Rhetores Latini minores (1863);
Quintilian (1868);
Sulpicius Severus (1866);
Minucius Felix together with
Firmicus Maternus De errore (1867);
Salvianus (1877) and
Victor Vitensis's
Historia persecutionis Africanae provinciae (1878). He was also an enthusiastic collector of
autographs. ==Scholarly shorthand==