Dealing with a time span of seven centuries, Livy did not use primary sources but relied on the work of previous historians. For the crossing of the Alps, he made extensive use of the Greek writer Polybius (c.200 – 118 B.C.) or of a lost, earlier Greek account that Polybius himself, who had also interviewed men who had been with Hannibal, had drawn upon. Polybius and Livy’s accounts can be read side by side in English translation on the livius.org site.
Livy occasionally failed to understand the original Greek fully. This illustration (from Two Centuries of Roman Prose, pg. 208) shows how Livy misinterpreted Polybius’s account of a landslip that delayed Hannibal’s descent.
Livy, but not Polybius, describes how the Carthaginians split a rock that was blocking their path by heating it and pouring on vinegar, which may have been mixed with water for soldiers to drink and was probably carried in amphorae like these. Some scholars have doubted the story but the acidity of vinegar means it can help fracture certain types of rocks, as explained in an article by archaeologist Pat Hunt.
Livy never became as much a public celebrity as did Virgil but his ambitious historical project was well known and one man is said to have traveled all the way to Italy from Cadiz in Spain just to see him, and, having done that, immediately returned home. Livy has remained a popular author for reading in schools and universities and the best-known stories from Rome’s early history are usually retold in the form he gave them.